FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“HEADPHONE AND ACOUSTIC CHARACTERISTIC ADJUSTMENT METHOD”
SONY CORPORATION, of 1-7-1, Konan, Minato-ku, Tokyo 108-0075, Japan
The following specification particularly describes the invention and the manner in which it is to
be performed.
2
Description
Title of Invention
HEADPHONE AND ACOUSTIC CHARACTERISTIC ADJUSTMENT METHOD
5
Technical Field
[0001]
The present disclosure relates to a headphone and an acoustic characteristic
adjustment method.
10
Background Art
[0002]
In general, headphones generate sounds when a driver unit that is disposed
in a housing drives a vibration plate according to an audio signal to vibrate air.
15 Here, acoustic characteristics of headphones are known to depend on a structure of a
housing. Specifically, acoustic characteristics of headphones can change according
to a volume of a space provided in the housing, a size of a vent hole that is formed in
the housing and is capable of serving as a passage of air, a size of an opening that is
formed on a partition wall of the housing and is capable of serving as a passage of air
20 between the inside and the outside of the housing, and the like. Thus, there are a
number of technologies proposed in relation to structures of housings in order to
improve acoustic characteristics.
[0003]
For example, Patent Literature 1 discloses a technology for improving
25 acoustic characteristics by providing a tubular duct unit which spatially connects the
inside and the outside of a housing on a rear side of the housing that is the opposite
side to the side on which a vibration plate of a driver unit is provided.
Citation List
30 Patent Literature
[0004]
3
Patent Literature 1: JP H4-227396A
Summary of Invention
Technical Problem
5 [0005]
However, demands for acoustic characteristics, e.g., for emphasis of an
output of sounds of a lower register, and the like, differ according to applications of
headphones. Thus, a desired acoustic characteristic is not necessarily obtained
when the technology disclosed in Patent Literature 1 above is applied to headphones.
10 [0006]
Therefore, the present disclosure proposes a novel and improved headphone
and acoustic characteristic adjustment method which can further improve acoustic
characteristics.
15 Solution to Problem
[0007]
According to the present disclosure, there is provided a headphone
including: a driver unit including a vibration plate; a housing configured to house the
driver unit, to form an air-tightened front air chamber of which a part except for an
20 opening for sound output is spatially blocked from the outside on a front side on
which the vibration plate of the driver unit is provided, and to form a rear air
chamber that has a predetermined capacity on a rear side that is the opposite side to
the front side; and an acoustic tube provided in a partial region of a partition wall of
the housing that constitutes the rear air chamber and configured to spatially connect
25 the rear air chamber and the outside of the housing through a tube.
[0008]
According to the present disclosure, there is provided an acoustic
characteristic adjustment method including: housing a driver unit that includes a
vibration plate in a housing, forming an air-tightened front air chamber of which a
30 part except for an opening for sound output is spatially blocked from the outside
between the housing and a front side on which the vibration plate of the driver unit is
4
provided, and forming a rear air chamber that has a predetermined capacity on a rear
side that is the opposite side to the front side; and providing an acoustic tube
provided in a partial region of a partition wall of the housing that constitutes the rear
air chamber and configured to spatially connect the rear air chamber and the outside
of the housing 5 through a tube.
[0009]
According to the present disclosure, by providing an acoustic tube that
spatially connects a rear air chamber in a housing and the outside of the housing
through a tube, a parallel resonance circuit is formed at least with capacitance that
10 corresponds to the volume of the rear air chamber and inductance that corresponds to
an inductance component with respect to a flow of air of the acoustic tube in an
acoustic equivalent circuit. Thus, a sound pressure level characteristic can be
adjusted using anti-resonance in the parallel resonance circuit. Since a parameter
for adjusting the sound pressure level characteristic increases, it is easier to realize a
15 desired sound pressure level characteristic, and thus an acoustic characteristic can be
further improved.
Advantageous Effects of Invention
[0010]
20 According to the present disclosure described above, acoustic characteristics
can be further improved. Note that the effect is not necessarily limitative, and along
with or instead of the effect, any effect disclosed in the present specification or any
other effect that can be understood from the present specification may be exhibited.
25 Brief Description of Drawings
[0011]
[FIG. 1] FIG. 1 is a schematic diagram showing an outline configuration of a
headphone according to an embodiment of the present disclosure.
[FIG. 2] FIG. 2 is a diagram showing an acoustic equivalent circuit of the headphone
30 shown in FIG. 1.
[FIG. 3] FIG. 3 is a graph diagram qualitatively showing sound pressure level
5
characteristics of the headphone according to the embodiment.
[FIG. 4A] FIG. 4A is a hexahedral diagram showing the external appearance of the
headphone according to the embodiment.
[FIG. 4B] FIG. 4B is a hexahedral diagram showing the external appearance of the
headphone according 5 to the embodiment.
[FIG. 4C] FIG. 4C is a hexahedral diagram showing the external appearance of the
headphone according to the embodiment.
[FIG. 4D] FIG. 4D is a hexahedral diagram showing the external appearance of the
headphone according to the embodiment.
10 [FIG. 4E] FIG. 4E is a hexahedral diagram showing the external appearance of the
headphone according to the embodiment.
[FIG. 4F] FIG. 4F is a hexahedral diagram showing the external appearance of the
headphone according to the embodiment.
[FIG. 5] FIG. 5 is an illustrative diagram showing an example of the headphone
15 according to the embodiment that is worn by a user.
[FIG. 6] FIG. 6 is a cross-sectional diagram showing a configuration of the
headphone according to the embodiment.
[FIG. 7] FIG. 7 is an exploded perspective diagram showing a configuration of the
headphone according to the embodiment.
20 [FIG. 8A] FIG. 8A is an exploded perspective diagram showing a configuration of a
modified example of the headphone of the embodiment in which the shape of an
acoustic tube is changed.
[FIG. 8B] FIG. 8B is an exploded perspective diagram showing a configuration of a
modified example of the headphone of the embodiment in which the way that a cable
25 is drawn into an inner space of a cable housing is changed.
[FIG. 8C] FIG. 8C is an exploded perspective diagram showing a configuration of a
modified example of the headphone of the embodiment in which the way that a cable
is drawn into an inner space of a cable housing is changed.
[FIG. 9] FIG. 9 is a graph diagram showing sound pressure level characteristics of the
30 headphone according to the embodiment.
[FIG. 10] FIG. 10 is a graph diagram for describing an effect of an acoustic resistance
6
Rd in the sound pressure level characteristic of the headphone according to the
embodiment.
[FIG. 11A] FIG. 11A is a hexahedral diagram showing the external appearance of a
headphone according to a modified example of the embodiment.
[FIG. 11B] FIG. 11B is a hexahedral diagram showing the external 5 appearance of a
headphone according to a modified example of the embodiment.
[FIG. 11C] FIG. 11C is a hexahedral diagram showing the external appearance of a
headphone according to a modified example of the embodiment.
[FIG. 11D] FIG. 11D is a hexahedral diagram showing the external appearance of a
10 headphone according to a modified example of the embodiment.
[FIG. 11E] FIG. 11E is a hexahedral diagram showing the external appearance of a
headphone according to a modified example of the embodiment.
[FIG. 11F] FIG. 11F is a hexahedral diagram showing the external appearance of a
headphone according to a modified example of the embodiment.
15 [FIG. 12A] FIG. 12A is a cross-sectional diagram of one cross-section of the
headphone according to the modified example.
[FIG. 12B] FIG. 12B is a cross-sectional diagram of one cross-section of the
headphone according to the modified example.
[FIG. 13A] FIG. 13A is a cross-sectional diagram of another cross-section of the
20 headphone according to the modified example.
[FIG. 13B] FIG. 13B is a cross-sectional diagram of another cross-section of the
headphone according to the modified example.
[FIG. 14] FIG. 14 is a cross-sectional diagram of still another cross-section of the
headphone according to the modified example.
25 [FIG. 15] FIG. 15 is a perspective diagram showing a configuration of a switch
member mounted in the headphone according to the modified example.
[FIG. 16] FIG. 16 is a graph diagram showing sound pressure level characteristics of
the headphone according to the modified example.
[FIG. 17] FIG. 17 is an illustrative diagram for describing an acoustic characteristic
30 adjustment mechanism having a mechanism that changes a length and an inner
diameter of an acoustic tube.
7
Description of Embodiments
[0012]
Hereinafter, (a) preferred embodiment(s) of the present disclosure will be
described in detail with reference to the appended drawings. In 5 this specification
and the appended drawings, structural elements that have substantially the same
function and structure are denoted with the same reference numerals, and repeated
explanation of these structural elements is omitted.
[0013]
10 Note that description will be provided in the following order.
1. Overview of an embodiment of the present disclosure
2. Configuration of a headphone according to the present embodiment
3. Acoustic characteristics of the headphone according to the present
embodiment
15 4. Acoustic tube design method
5. Modified example
6. Supplement
[0014]
(1．Overview of an embodiment of the present disclosure)
20 An overview of an embodiment of the present disclosure will be described
with reference to FIGS. 1 to 3. First, a schematic configuration of a headphone of
the present embodiment will be described with reference to FIG. 1. Next, an
acoustic equivalent circuit of the headphone of the present embodiment will be
described with reference to FIG. 2. Further, acoustic characteristics realized
25 through the present embodiment will be described qualitatively with reference to FIG.
3.
[0015]
First, the schematic configuration of the headphone according to the
embodiment of the present disclosure will be described with reference to FIG. 1.
30 FIG. 1 is a schematic diagram showing the schematic configuration of the headphone
according to the embodiment of the present disclosure. Referring to FIG. 1, the
8
headphone 10 according to the present embodiment is provided with a driver unit
110 and a housing 140 that houses the driver unit 110. FIG. 1 shows a cross-section
of the headphone 10 passing substantially the center of the driver unit 110. In
addition, in FIG. 1, only principal constituent members among constituent members
of the headphone 10 of the present embodiment are schematically 5 shown for the sake
of simplification. In addition, in order to show a correspondence between the
constituent members of the headphone 10 and elements of the acoustic equivalent
circuit shown in FIG. 2, reference symbols of the elements of the acoustic equivalent
circuit are affixed to several reference numerals given to the constituent members in
10 FIG. 1.
[0016]
The driver unit 110 has a frame 111, a vibration plate 112, a magnet 113, a
plate 114, and a voice coil 115. The frame 111 has a substantial disc shape, and the
magnet 113, the plate 114, the voice coil 115, and the vibration plate 112 are placed
15 on one surface side of the disc shape. The frame 111 has a projecting part
substantially at the center part thereof that projects on the opposite side to the side on
which the magnet 113, the plate 114, the voice coil 115, and the vibration plate 112
are provided. The magnet 113, the plate 114, and the voice coil 115 have a
cylindrical shape and are placed inside the projecting part substantially in a
20 concentric shape with the frame 111. The magnet 113 is interposed between the
frame 111 and the plate 114. The voice coil 115 is placed on a further outer
circumferential side than the magnet 113 and the plate 114. The vibration plate 112
is provided to cover one surface of the frame 111, and some regions thereof are
connected to the voice coil 115. When the voice coil 115 is driven according to an
25 audio signal supplied from outside by, for example a cable (not illustrated) or the like
in a magnetic field generated by the magnet 113, the vibration plate 112 vibrates in
the thickness direction. Here, the audio signal refers to an electric signal on which
information of a sound is overlaid, and when the vibration plate 112 vibrates
according to an audio signal, ambient air becomes sparse or dense, and thus a sound
30 corresponding to the audio signal is generated.
[0017]
9
Here, in the description below, the center axis direction of the disc shape of
the driver unit 110 will be referred to as a z axis direction. In addition, the side on
which the vibration plate 112 is provided when it is viewed from the driver unit 110
will be referred to as a front side, and the direction on the front side in the z axis
direction will be referred to as a forward direction or a front side 5 direction of the z
axis. In addition, the opposite side to the front side will be referred to as a rear side,
and the direction on the rear side in the z axis direction will be referred to as a
backward direction or a rear direction of the z axis. In addition, two directions that
are orthogonal to each other within the plane that is orthogonal to the z axis direction
10 will be referred to as an x axis direction and a y axis direction.
[0018]
In the present embodiment, the voice coil 115 has a cylindrical shape. In
the vibration plate 112, a region positioned on the inner side of the voice coil 115
will also be referred to as a dome part, and a region positioned on the outer side of
15 the voice coil 115 will also be referred to as an edge part. Likewise, in the frame
111, a region positioned on the inner side of the voice coil 115 (region corresponding
to the projecting part) will also be referred to as a dome part, and a region positioned
on the outer side of the voice coil 115 (region corresponding to a flange part on a
circumference of the projecting part) will also be referred to as an edge part. For
20 the sake of convenience in the description below, in the space between the frame 111
and the vibration plate 112 (which will be referred to as a driver unit rear air chamber
118 hereinbelow), the space formed on the inner side of the voice coil 115 will also
be referred to as a dome part, and the space formed on the outer side of the voice coil
115 will also be referred to as an edge part.
25 [0019]
The frame 111 of the driver unit 110 is provided with a vent hole 116 that
passes through the frame 111 in the z axis direction, and the driver unit rear air
chamber 118 is spatially connected to the space which is a space on the rear side of
the driver unit 110 and is surrounded by the driver unit 110 and the housing 140 (a
30 rear air chamber 132 to be described below) through the vent hole 116. In the
example shown in FIG. 1, the vent hole 116 is formed substantially at the center of
10
the frame 111, spatially connecting the dome part of the driver unit rear air chamber
118 and the rear air chamber 132.
[0020]
The vent hole 116 is provided with a ventilation resistor 117 to plug the hole.
The ventilation resistor 117 is formed of, for example, compressed 5 urethane, nonwoven
fabric, or the like, and acts as a resistive component to a flow of air.
However, a material of the ventilation resistor 117 is not limited thereto, and any
material that can exert predetermined resistance to a flow of air can be used.
[0021]
10 Here, in the present embodiment, an element that has relatively small
resistance to a flow of air can be selected as the ventilation resistor 117. Due to the
relatively small resistance of the ventilation resistor 117 to a flow of air, air between
the driver unit rear air chamber 118 and the rear air chamber 132 flows relatively
freely. However, as will be described below with reference to FIGS. 2 and 3,
15 resistance Rd for the resistive component of the ventilation resistor 117 in an
acoustic equivalent circuit 40 is linked to a sound pressure level characteristic of the
headphone 10. In addition, as will be described in (3. Acoustic characteristics of the
headphone according to the present embodiment) below, when the ventilation resistor
117 is not provided (in other words, when the resistance Rd is zero), acoustic
20 characteristics of the headphone 10 remarkably change. Thus, a characteristic with
regard to ventilation resistance, such as a material of the ventilation resistor 117, can
be appropriately selected in reality when taking the influence of the resistance Rd on
the acoustic characteristics of the headphone 10 into account.
[0022]
25 Note that, in the example shown in FIG. 1, although the vent hole 116 is
provided in the region corresponding to the dome part of the frame 111, a position in
the frame 111 at which the vent hole 116 is provided is not limited thereto. In the
present embodiment, it is desirable that the vent hole 116 be provided to spatially
connect the driver unit rear air chamber 118 and the rear air chamber 132. For
30 example, the vent hole 116 may be formed at a position deviated from the center of
the frame 111 only a predetermined distance in the radial direction (i.e., the edge
11
part). In addition, a plurality of vent holes 116 may be provided at different
positions in the frame 111. As will be described below with reference to FIG. 2, the
ventilation resistor 117 provided in the vent hole 116 functions as the resistance Rd
that affects acoustic characteristics in the acoustic equivalent circuit 40 of the
headphone 10. In the present embodiment, the position at which 5 the vent hole 116
is provided in the frame 111 may be a position in the acoustic equivalent circuit 40 at
which the ventilation resistor 117 provided in the vent hole 116 has the same
function, and may be appropriately set when taking, for example, disposed positions
of other constituent members within the housing 140 into account.
10 [0023]
In addition, the driver unit 110 according to the present embodiment may be
a so-called dynamic driver unit. As such a driver unit 110, an existing general
dynamic driver unit can be applicable. With regard to disposed positions of the
frame 111, the vibration plate 112, the magnet 113, the plate 114, and the voice coil
15 115 or a driving method of the driver unit 110, for example, disposed positions or a
driving method of these members in a general dynamic driver unit may be applied.
The driver unit 110 according to the present embodiment, however, is not limited to a
dynamic driver unit, and may be a driver unit of another type. For example, the
driver unit 110 may be a so-called balanced armature driver unit (a BA driver unit).
20 Even if the driver unit 110 is a BA driver unit in the present embodiment, the same
effect as that obtained when the driver unit is a dynamic driver unit to be described
below can be obtained.
[0024]
The housing 140 houses the driver unit 110. A front air chamber 125 that
25 is a space surrounded by the driver unit 110 and the housing 140 is formed on the
front side of the driver unit 110. In addition, the rear air chamber 132 that is a space
surrounded by the driver unit 110 and the housing 140 is formed on the rear side of
the driver unit 110.
[0025]
30 The housing 140 may be composed of a plurality of members. In the
example shown in FIG. 1, the housing 140 is formed by bonding a front housing 120
12
that covers the front side of the driver unit 110 and a rear housing 130 that covers the
rear side of the driver unit 110. Note that the present embodiment is not limited
thereto, and the housing 140 may be composed of three or more members.
[0026]
Openings 121 and 122 which spatially connect the inside 5 and the outside of
the housing 140 are provided in a partition wall of the front housing 120. The
opening 121 is a sound output opening for outputting a sound to the outside. Air
inside the front air chamber 125 is output to the outside via the opening 121 as a
sound. A sound guiding tube 124 which is a tubular portion protruding to the
10 outside is formed in a partial region of the front housing 120, and the opening 121 is
provided at the tip of the sound guiding tube 124. When a user listens to a sound,
the tip of the sound guiding tube 124 is inserted into an external auditory canal of the
user. As described above, the headphone 10 of the present embodiment may be a
so-called canal earphone. Note that an earpiece (not illustrated) for bringing the
15 sound guiding tube 124 in close contact with the inner wall of the external auditory
canal of a user may be provided in the outer circumference of the tip of the sound
guiding tube 124. In addition, an equalizer (not illustrated) which is a ventilation
resistor may be provided inside the sound guiding tube 124. By setting a material
and a shape of the equalizer appropriately, adjustment of sound quality, for example,
20 reducing an output of a sound of a specific frequency band, or the like, can be
performed.
[0027]
A ventilation resistor 123 is provided in the opening 122 to plug the hole
thereof. The ventilation resistor 123 has the same function as the ventilation
25 resistor 117 described above. In the present embodiment, however, a material and a
shape of the ventilation resistor 123 are selected to substantially block air. As
described, in the present embodiment, the front air chamber 125 except for the
opening 121 may be spatially blocked from the outside with regard to a flow of air.
In the description below, the front air chamber 125 except for the opening 121 for
30 sound output that is formed to be spatially blocked from the outside with regard to a
flow of air will also be referred to as an enclosed front air chamber 125. In addition,
13
the headphone 10 with the enclosed front air chamber 125 will also be referred to as
an enclosed headphone 10.
[0028]
An acoustic tube 150 which is formed of a tubular member and spatially
connects the rear air chamber 132 and the outside of the housing 140 5 (i.e., the outside
of the headphone 10) through a tube is provided in a partial region of the partition
wall of the rear housing 130. The acoustic tube 150 is provided, for example,
projecting toward the outside from the partition wall of the rear housing 130 as
shown in FIG. 1. Here, the acoustic tube 150 is formed to have a length and an
10 inner cross-sectional area (a cross-sectional area of the tube inner part regulated by
the inner diameter of the acoustic tube 150) in which a predetermined inductance
component acts on a flow of air passing through the inside of the acoustic tube 150.
As will be described below with reference to FIG. 2, in the present embodiment, the
inductance component of the acoustic tube 150 acting on the flow of air functions as
15 inductance Mb acting on acoustic characteristics in the acoustic equivalent circuit 40
of the headphone 10. Note that a specific configuration and shape of the acoustic
tube 150 will be described in detail in (4. Acoustic tube design method) below.
[0029]
In addition, in the present embodiment, an opening that spatially connects
20 the rear air chamber 132 and the outside of the housing 140 may not be provided in
the region of the partition wall of the rear housing 130 other than the region in which
the acoustic tube 150 is provided. Thus, the rear air chamber 132 can be spatially
blocked from the outside except for ventilation in the acoustic tube 150. In order to
realize such a configuration, the joining part of the front housing 120 and the rear
25 housing 130 is joined in a state in which, for example, air tightness is maintained
using an adhesive or the like. Note that the influence caused by providing an
opening other than the acoustic tube 150 in the partition wall of the rear housing 130
(which corresponds to providing housing resistance to be described below) on the
acoustic characteristics of the headphone 10 will be described in detail in (3.
30 Acoustic characteristics of the headphone according to the present embodiment)
below.
14
[0030]
The acoustic tube 150 is formed such that, for example, a tubular member is
prepared separately from the housing 140 and the tubular member and the housing
140 are combined. For example, the acoustic tube 150 is configured such that an
opening which spatially connects the rear air chamber 132 and 5 the outside of the
housing 140 is provided in a partial region of the partition wall of the housing 140
that forms the rear air chamber 132 and the tubular member is connected to the
opening. Specifically, the tubular member of the acoustic tube 150 may be
provided so as to pass through the opening so that one end thereof is positioned
10 inside the rear air chamber 132 and the other end is positioned outside of the housing
140. In addition, the acoustic tube 150 may be configured such that one end of the
tubular member is connected to the opening. In the present embodiment as
described above, however, the rear air chamber 132 can be spatially blocked from the
outside except for ventilation in the acoustic tube 150, and thus, with regard to the
15 opening provided in the partition wall of the housing 140 connected to the tubular
member, the joining part of the opening and the tubular member is joined in a state in
which, for example, air tightness is maintained using an adhesive or the like.
[0031]
In addition, for example, the acoustic tube 150 may be formed integrated
20 with the housing 140. If the acoustic tube 150 is formed integrated with the
housing 140, it is not necessary to form an opening to be connected to the tubular
member in the partition wall of the housing 140, and thus air tightness of the rear air
chamber 132 can be secured more reliably.
[0032]
25 The schematic configuration of the headphone 10 according to the present
embodiment has been described above with reference to FIG. 1. Next, the acoustic
equivalent circuit of the headphone 10 shown in FIG. 1 will be described with
reference to FIG. 2. FIG. 2 is a diagram showing the acoustic equivalent circuit of
the headphone 10 shown in FIG. 1.
30 [0033]
Here, the acoustic equivalent circuit refers to a circuit obtained by replacing
15
elements of the mechanical system and the acoustic system of the headphone 10 with
elements of an electrical circuit. In the acoustic equivalent circuit, a voltage thereof
corresponds to sound pressure in the acoustic system, and a current thereof
corresponds to a particle velocity of air (in other words, a flow of air) in the acoustic
system. Thus, by analyzing a voltage of the acoustic equivalent 5 circuit of the
headphone 10, sound pressure of a sound output from the headphone 10 can be
analyzed. Here, a ratio of sound pressure of an output sound to a reference value
(for example, a minimum value of audible sound pressure of a person) expressed in
the unit of decibels is referred to as a sound pressure level (SPL), which is one index
10 for evaluating acoustic characteristics. Adjusting a sound pressure level
characteristic can be said to be, in other words, adjusting an acoustic characteristic.
By calculating a sound pressure level of the headphone 10 from the acoustic
equivalent circuit, an acoustic characteristic of the headphone 10 can be evaluated.
[0034]
15 Referring to FIG. 2, a signal source Vs, inductance Mo, resistance Ro, and
capacitance Co are arranged in series in the acoustic equivalent circuit 40. The
signal source Vs, the inductance Mo, the resistance Ro, and the capacitance Co are
elements corresponding to the elements of the mechanical system of the driver unit
110. Specifically, the signal source Vs is an element corresponding to vibratory
20 force when the driver unit 110 causes the vibration plate 112 to vibrate, and is a
power source element that generates electromotive force in the acoustic equivalent
circuit 40. In addition, the inductance Mo, the resistance Ro, and the capacitance
Co are elements respectively corresponding to a mass, mechanical resistance, and
compliance of the driver unit 110.
25 [0035]
In addition, resistance Rl and capacitance Cl are arranged in parallel in the
acoustic equivalent circuit 40. Here, the resistance Rl and the capacitance Cl are
elements relating to a flow of air in the front air chamber 125. Specifically, the
resistance Rl corresponds to a resistive component of the ventilation resistor 123
30 provided in the opening 122 of the front air chamber 125. In the present
embodiment as described above, the front air chamber 125 is an air-tightened type,
16
and thus the resistance Rl can be deemed as having a sufficiently large value. In
addition, the capacitance Cl corresponds to the volume of the front air chamber 125.
[0036]
In addition, in the acoustic equivalent circuit 40, capacitance Cd,
capacitance Cb, and inductance Mb are arranged in parallel. In 5 addition, resistance
Rd is present between the capacitance Cd and the capacitance Cb that are arranged in
parallel. Here, the resistance Rd, the capacitance Cd, the capacitance Cb, and the
inductance Mb are elements relating to a flow of air in the driver unit rear air
chamber 118 and the rear air chamber 132. Specifically, the resistance Rd
10 corresponds to the resistive component of the ventilation resistor 117 that is provided
in the vent hole 116 which spatially connects the driver unit rear air chamber 118 and
the rear air chamber 132. In addition, the capacitance Cd and the capacitance Cb
respectively correspond to the volumes of the driver unit rear air chamber 118 and
the rear air chamber 132. In addition, the inductance Mb corresponds to an
15 inductance component of the acoustic tube 150. As will be described with
reference to FIG. 3, by changing values of the resistance Rd, the capacitance Cd, the
capacitance Cb, and the inductance Mb here in the present embodiment, the acoustic
characteristics of the headphone 10 are adjusted. Hereinbelow, the resistance Rd
will also be referred to as an acoustic resistance, the capacitance Cb as an acoustic
20 capacity, and the inductance MB as an acoustic inductance.
[0037]
Here, focusing on the capacitance Cb and the inductance Mb, it can be
assumed that a parallel resonance circuit that causes anti-resonance at a
predetermined resonance frequency is formed at least with the capacitance Cb and
25 the inductance Mb in the acoustic equivalent circuit 40. In the present embodiment,
as anti-resonance occurs due to an acoustic capacity and an acoustic inductance, a
sound pressure level in a predetermined frequency band can be adjusted.
[0038]
Note that, since one having a relatively small resistance (in other words, a
30 value of the resistance Rd may be relatively small) to a flow of air may be selected as
the ventilation resistor 117 in the present embodiment as described above, air can
17
flow relatively freely between the driver unit rear air chamber 118 and the rear air
chamber 132. In this case, the acoustic capacity described above may further
include the capacitance Cd that is a capacity component corresponding to the volume
of the driver unit rear air chamber 118. Thus, it can be assumed that, when a value
of the resistance Rd is relatively small, a parallel resonance circuit 5 that causes antiresonance
at a predetermined resonance frequency is formed approximately with the
inductance Mb and combined capacitance Cs of the capacitance Cd and the
capacitance Cb. In this manner, anti-resonance can be said to occur due to the
capacitance Cd, the capacitance Cb, and the inductance Mb in the present
10 embodiment. In description below, an acoustic capacity may be the capacitance Cb,
and may further include the capacitance Cd.
[0039]
Adjustment of a sound pressure level using anti-resonance caused by an
acoustic capacity and an acoustic inductance will be described in detail with
15 reference to FIG. 3. FIG. 3 is a graph diagram qualitatively showing sound pressure
level characteristics of the headphone 10 according to the embodiment. In FIG. 3,
the horizontal axis represents frequency, the vertical axis represents sound pressure
level, and sound pressure level characteristics of the headphone 10 obtained from the
analysis result of the acoustic equivalent circuit 40 shown in FIG. 2 are plotted. In
20 addition, in the example shown in FIG. 3, the acoustic capacity includes the
capacitance Cb and the capacitance Cd.
[0040]
First, a desired acoustic characteristic in the present embodiment will be
described with reference to FIG. 3. For the sake of convenience in the description
25 below, the frequency band equal to or lower than 200 (Hz) will be referred to as a
lower register, the frequency band from 200 (Hz) to 2000 (Hz) will be referred to as
a middle register, and the frequency band equal to or higher than 2000 (Hz) will be
referred to as an upper register. If frequency bands are divided as above, for
example, a voice of a person belongs to the middle register, and a bass note lower
30 than that belongs to the lower register.
[0041]
18
An example of a desired acoustic characteristic in the present embodiment is
realized by, for example, a sound pressure level characteristic in which a sound of the
lower register is more emphasized and sound quality of a sound of the middle
register is more improved. Emphasizing a sound of a lower register more can be
realized by, for example, setting the front air chamber 125 of the 5 headphone 10 to be
an air-tightened type. For example, it is known that, in a headphone having an airtightened
front air chamber, such as a canal earphone, a sound can be output in a
state in which predetermined sound pressure is maintained up to an even lower
frequency band. FIG. 3 shows an example of the sound pressure level characteristic
10 of an existing general headphone of an air-tightened type using the dotted curve A.
[0042]
Meanwhile, it is known with regard to the quality of a sound of the middle
register that, for example, if sound pressure significantly changes in a frequency
band of the middle register in which a voice of a person is included, a user who hears
15 the sound feels that the voice of the person is like a muffled sound. Thus, in order
to improve the quality of a sound of the middle register, it is desirable to cause a
sound pressure level of the middle register to undergo a relatively small change.
[0043]
Thus, a sound pressure level characteristic in which the quality of a sound of
20 the middle register is improved while a sound of a lower register is more emphasized
can be considered to be a sound pressure level characteristic in which, so to speak, a
sound pressure level decreases from the lower register to the middle register in a stair
pattern (hereinafter referred to simply as a “stair-like sound pressure level
characteristic”), e.g., sound pressure decreases from the lower register to the middle
25 register with a steep slope and a sound pressure level changes as little as possible in
the middle register. Here, referring to the curve A shown in FIG. 3, in a sound
pressure level characteristic of an existing headphone, sound pressure decreases from
the lower register to the middle register with a relatively gentle slope, and the
decreased sound pressure level is maintained with the gentle slope in the middle
30 register. In such a sound pressure level characteristic, there is concern of high
sound quality not being realized for, for example, a voice of a person that is included
19
in the middle register. As described above, with regard to existing headphones of
the air-tightened type, a sound pressure level characteristic in the middle register, in
particular, has room for improvement.
[0044]
Here, it is known for an existing headphone that a sound pressure 5 level of a
predetermined frequency band is decided based at least on a value of ventilation
resistance between the driver unit rear air chamber and the space on the rear side of
the driver unit (i.e., which corresponds to the resistive component of the ventilation
resistor 117 shown in FIG. 1 and the resistance Rd shown in FIG. 2 in the present
10 embodiment). Specifically, by changing the value of the resistance Rd
corresponding to the ventilation resistance, a value of a sound pressure level can be
adjusted from the lower register to the middle register. Thus, by changing the value
of the resistance Rd, there is a possibility of a sound pressure level in the middle
register being adjusted and the acoustic characteristics being improved. However,
15 when the value of the resistance Rd changes as indicated by the arrow in FIG. 3, the
value of the sound pressure level fluctuates with the maintained slope of the curve A.
Even if it is attempted to improve an acoustic characteristic by adjusting, for example,
the value of the resistance Rd in an existing headphone it is difficult to obtain the
above-described stair-like sound pressure level characteristic.
20 [0045]
Meanwhile, in the present embodiment, a parallel resonance circuit that
causes anti-resonance with an acoustic capacity and an acoustic inductance is formed
by providing the acoustic tube 150. Anti-resonance in the acoustic equivalent
circuit 40 acts to form a dip of the sound pressure level in the sound pressure level
25 curve shown in FIG. 3. For example, FIG. 3 illustrates the curve B having a dip in
the middle register using a solid line. The dip corresponds to anti-resonance caused
by the acoustic capacity and the acoustic inductance. Here, a resonance frequency
fh of the anti-resonance can be decided based at least on a value of the acoustic
capacity and a value of the acoustic inductance. In the present embodiment, by
30 adjusting the value of the acoustic capacity and the value of the acoustic inductance,
the frequency band in which the resonance frequency fh of the anti-resonance is
20
included, i.e., the frequency band in which the dip of the sound pressure level is
formed, can be adjusted.
[0046]
In addition, the driver unit 110 according to the present embodiment may
have the same configuration as an existing general dynamic driver 5 unit as described
above. Thus, in the present embodiment, a sound pressure level in a predetermined
frequency band can also be decided based at least on a value of the resistance Rd (i.e.,
acoustic resistance), like an existing headphone. Specifically, in the present
embodiment, a value of the sound pressure level can be adjusted from the lower
10 register to the middle register by changing a value of the acoustic resistance. Thus,
by appropriately adjusting the value of the acoustic capacity and the value of the
acoustic inductance so that the resonance frequency fh of anti-resonance is
positioned in the frequency band from the lower register to the middle register, the
value of the sound pressure level from the lower register to the middle register can be
15 the sum of a change of the value caused by the acoustic resistance and a change of
the value caused by the dip formed due to the anti-resonance. Thus, a step of the
sound pressure level with a steeper slope than the slope shown by the curve A can be
formed in the frequency band in which the resonance frequency fh is positioned, i.e.,
the frequency band in which the dip is formed.
20 [0047]
As described above, in the present embodiment, the sound pressure level of
the headphone 10 in a predetermined frequency band can be decided based at least
on a value of the acoustic capacity, a value of the acoustic inductance, and a value of
the acoustic resistance. Specifically, the sound pressure level from the lower
25 register to the middle register can be adjusted using the acoustic capacity, the
acoustic inductance, and the acoustic resistance. In addition, since the front air
chamber 125 is the air-tightened type in the present embodiment, the sound pressure
level characteristic in which the sound pressure level in the lower register is
maintained at a higher value than the sound pressure level in the middle register can
30 be realized. Thus, by appropriately adjusting the values of the acoustic capacity, the
acoustic inductance, and the acoustic resistance, for example, the above-described
21
stair-like sound pressure level characteristic can be obtained. In addition, by further
appropriately adjusting the values of the acoustic capacity, the acoustic inductance,
and the acoustic resistance, the difference of the sound pressure levels in the lower
register and the middle register and the frequency band in which the step formed
when the sound pressure level decreases in the stair pattern 5 is positioned can be
adjusted. Thus, a fluctuating acoustic characteristic in which the difference in the
levels in the lower register and the middle register is significant is realized.
[0048]
In FIG. 3, an example of the stair-like sound pressure level characteristic
10 obtained in the present embodiment is illustrated using the dashed curve C. In the
sound pressure level characteristic indicated by the dashed curve C, for example,
values of the acoustic capacity and the acoustic inductance can be appropriately
adjusted so that the resonance frequency fh of anti-resonance is positioned between
about 350 (Hz) and 650 (Hz). In addition, in the state in which the resonance
15 frequency fh is positioned between about 350 (Hz) and 650 (Hz), a value of the
acoustic resistance can be appropriately adjusted so that the sound pressure level
decreases with a steeper slope from the lower register to the middle register. In the
present embodiment as described above, as one desired acoustic characteristic, the
sound pressure level characteristic in which the quality of a sound of a middle
20 register is more improved while a sound of a lower register is more emphasized is
realized.
[0049]
Here, the acoustic capacity corresponds to, for example, the combined
capacitance of the capacitance Cb and the capacitance Cd as descried above. The
25 capacitance Cd corresponds to the volume of the driver unit rear air chamber 118,
and a value thereof can be decided according to the configuration of the frame 111
and the vibration plate 112 in the driver unit 110. In addition, the capacitance Cb
corresponds to the volume of the rear air chamber 132, and a value thereof can be
decided according to the configuration of the rear housing 130. In addition, the
30 acoustic inductance (inductance Mb) corresponds to the inductance component of the
acoustic tube 150, and a value thereof depends on the shape of the acoustic tube 150.
22
For example, as the inner cross-sectional area of the acoustic tube 150 decreases and
a length thereof increases, a value of the inductance Mb increases. In addition, the
acoustic resistance (resistance Rd) corresponds to the resistive component of the
ventilation resistor 117 provided in the vent hole 116 which spatially connects the
driver unit rear air chamber 118 and the rear air chamber 132, 5 and a value thereof
depends on a material and a shape of the ventilation resistor 117. For example, as
the material of the ventilation resistor 117 is packed with particles more densely, as a
length of the ventilation resistor 117 in the direction of a flow of air (the z axis
direction in the example shown in FIG. 1) is longer, and as the cross-sectional area of
10 the ventilation resistor 117 decreases, the value of the resistance Rd increases. In
this manner in the present embodiment, by changing the configuration of the rear
housing 130, the configurations of the frame 111 and the vibration plate 112 in the
driver unit 110, the shape of the acoustic tube 150, and the material and the shape of
the ventilation resistor 117, the values of the acoustic capacity, the acoustic
15 inductance, and the acoustic resistance can be changed and thus the desired sound
pressure level characteristic can be realized.
[0050]
(2. Configuration of a headphone according to the present embodiment)
Next, a configuration of a headphone according to an embodiment of the
20 present disclosure will be described in more detail with reference to FIGS. 4A to 4F,
5, 6, and 7. FIGS. 4A to 4F are hexahedral diagrams showing the external
appearance of the headphone according to the present embodiment. FIG. 5 is an
illustrative diagram showing an example of the headphone according to the present
embodiment that is worn by a user. FIG. 6 is a cross-sectional diagram showing a
25 configuration of the headphone according to the present embodiment. FIG. 7 is an
exploded perspective diagram showing a configuration of the headphone according
to the present embodiment.
[0051]
Referring to FIGS. 4A to 4F, 5, 6, and 7, the headphone 20 according to the
30 present embodiment is provided with a driver unit 210 and a housing 240 that houses
the driver unit 210. Here, the headphone 20 shown in FIGS. 4A to 4F, 5, 6, and 7
23
corresponds to the headphone 10 described with reference to FIG. 1. Thus, when
each of constituent members of the headphone 20 is described below, the
correspondence with each of constituent members of the headphone 10 shown in FIG.
1 will also be described. In addition, since the corresponding constituent members
have the same functions, constituent members of the headphone 5 20 that correspond
to the constituent members described above with reference to FIG. 1 will not be
described in detail.
[0052]
First, the external appearance of the headphone 20 according to the present
10 embodiment will be described with reference to FIGS. 4A to 4F and 5. Referring to
FIGS. 4A to 4F, the housing 240 of the headphone 20 according to the present
embodiment can be composed of a plurality of members. The housing 240
corresponds to the housing 140 shown in FIG. 1. In the example shown in FIGS.
4A to 4F, the housing 240 is composed of three components. In other words, the
15 housing 240 is composed of a front housing 220 which covers the front side of the
driver unit 210, a rear housing 230 which covers the rear side of the driver unit 210,
and a cable housing 290 which covers a cable 291 that supplies audio signals to the
driver unit 210. The front housing 220 and the rear housing 230 respectively
correspond to the front housing 120 and the rear housing 130 shown in FIG. 1.
20 Note that the present embodiment is not limited thereto, and the housing 240 may be
composed of four or more members.
[0053]
A sound guiding tube 224 that is a tubular portion protruding toward the
outside is formed in a partial region of the front housing 220. The sound guiding
25 tube 224 corresponds to the sound guiding tube 124 shown in FIG. 1. In addition,
an earpiece 226 for bringing the sound guiding tube 224 in close contact with the
inner wall of an external auditory canal of a user is provided in the outer
circumference of a tip of the sound guiding tube 224. An opening for sound output
(an opening 221 shown in FIG. 6) is provided inside the sound guiding tube 224, and
30 when a user listens to a sound, the tip of the sound guiding tube 224 including the
earpiece 226 is inserted into the external auditory canal of the user as shown in FIG.
24
5. As described above, the headphone 20 according to the present embodiment may
be the so-called canal earphone.
[0054]
Next, an inner configuration of the headphone 20 according to the present
embodiment will be described with reference to FIGS. 6 and 7. Here, 5 FIG. 6 shows
a cross-section that passes through substantially the center of the driver unit 210 of
the headphone 20. In addition, FIG. 7 shows an exploded state of a portion of the
cable housing 290 of the headphone 20 to illustrate the disposition of an acoustic
tube 250 and a cable 291 to be described below within the cable housing 290. Note
10 that constituent members illustrated in FIGS. 6 and 7 are simplified for the sake of
description of the present embodiment, and the headphone 20 may be further
provided with other constituent members that are not illustrated in the drawings.
Since the constituent members that are not illustrated may be known constituent
members of an existing general headphone, detailed description thereof will be
15 omitted. In addition, since the headphone 20 corresponds to the headphone 10
shown in FIG. 1 as described above, an acoustic equivalent circuit of the headphone
20 may be, for example, the same as the acoustic equivalent circuit 40 shown in FIG.
2. Thus, as in FIG. 1, reference symbols of elements of the acoustic equivalent
circuit 40 are affixed to several reference numerals given to the constituent members
20 of the headphone 20 in FIG. 6.
[0055]
The driver unit 210 has a frame 211, a vibration plate 212, a magnet 213, a
plate 214, and a voice coil 215. The driver unit 210 corresponds to the driver unit
110 shown in FIG. 1. In addition, the frame 211, the vibration plate 212, the magnet
25 213, the plate 214, and the voice coil 215 respectively correspond to the frame 111,
the vibration plate 112, the magnet 113, the plate 114, and the voice coil 115 shown
in FIG. 1. A driver unit rear air chamber 218 is formed between the driver unit 210
and the vibration plate 212. An element that corresponds to vibratory force
generated when the vibration plate 212 vibrates corresponds to a signal source Vs in
30 the acoustic equivalent circuit 40. In addition, a mass, mechanical resistance, and
compliance of the driver unit 210 respectively correspond to inductance Mo,
25
resistance Ro, and capacitance Co in the acoustic equivalent circuit 40.
Furthermore, the volume of the driver unit rear air chamber 218 corresponds to
capacitance Cd in the acoustic equivalent circuit 40. Note that the driver unit 210
according to the present embodiment may be a so-called dynamic driver unit, like the
driver unit 110 shown in FIG. 1. In the present embodiment, however, 5 a type of the
driver unit 210 is not limited, and the same effect can be obtained even if the driver
unit 210 is a driver unit of another type.
[0056]
A vent hole 216 that passes through the frame 211 in the z axis direction is
10 provided in the frame 211 of the driver unit 210. The vent hole 216 corresponds to
the vent hole 116 shown in FIG. 1. The vent hole 216 is provided substantially at
the center of the frame 211, and spatially connects the driver unit rear air chamber
218 and the space which is a space on the rear side of the driver unit 210 and is
surrounded by the driver unit 210 and the housing 240 (a rear air chamber 232 to be
15 described below).
[0057]
The vent hole 216 is provided with a ventilation resistor 217 that plugs the
hole. The ventilation resistor 217 corresponds to the ventilation resistor 117 shown
in FIG. 1. A resistive component of the ventilation resistor 217 to a flow of air
20 corresponds to resistance Rd in the acoustic equivalent circuit 40.
[0058]
Here, a material and a shape of the ventilation resistor 217 may be
appropriately set so that a desired sound pressure level characteristic is obtained
when taking, for example, the sound pressure level characteristic shown in FIG. 3
25 into consideration. More specifically, a material and a shape of the ventilation
resistor 217 can be appropriately set so that a value of the resistance Rd with which
the stair-like sound pressure level characteristic is obtained is realized as described
with reference to FIG. 3. For example, in the present embodiment, an element that
has relatively small resistance to a flow of air can be selected as the ventilation
30 resistor 217. Due to the relatively small resistance of the ventilation resistor 217 to
a flow of air, air between the driver unit rear air chamber 218 and the rear air
26
chamber 232 flows relatively freely. However, as described above with reference to
FIGS. 2 and 3, resistance Rd for the resistive component of the ventilation resistor
217 in an acoustic equivalent circuit 40 is linked to a sound pressure level
characteristic of the headphone 20. In addition, as will be described in (3. Acoustic
characteristics of the headphone according to the present embodiment) 5 below, when
the ventilation resistor 217 is not provided (in other words, when the resistance Rd is
zero), acoustic characteristics of the headphone 20 remarkably change. Thus, a
characteristic with regard to ventilation resistance, such as a material of the
ventilation resistor 217, can be appropriately selected in reality when taking the
10 influence of the resistance Rd on the acoustic characteristics of the headphone 20
into account.
[0059]
Note that, in the present embodiment, it is desirable that the vent hole 216
be provided to spatially connect the driver unit rear air chamber 218 and the rear air
15 chamber 232, and a position thereof to be formed is not limited to the example
shown in FIG. 6. For example, the vent hole 216 may be formed at a position
deviated from the center of the frame 211 only a predetermined distance in the radial
direction (i.e., the edge part). In addition, a plurality of vent holes 216 may be
provided at different positions in the frame 211. In the present embodiment, the
20 position at which the vent hole 216 is provided in the frame 211 may be a position in
the acoustic equivalent circuit 40 at which the ventilation resistor 217 provided in the
vent hole 216 has the same function, and may be appropriately set when taking, for
example, disposed positions of other constituent members within the housing 240
into account.
25 [0060]
The housing 240 houses the driver unit 210. The housing 240 corresponds
to the housing 140 shown in FIG. 1. A front air chamber 225 which is a space
surrounded by the driver unit 210 and the housing 240 is formed on the front side of
the driver unit 210. In addition, the rear air chamber 232 which is a space
30 surrounded by the driver unit 210 and the housing 240 is formed on the rear side of
the driver unit 210. The volume of the front air chamber 225 and the volume of the
27
rear air chamber 232 respectively correspond to capacitance Cl and capacitance Cb
in the acoustic equivalent circuit 40.
[0061]
As described above, the housing 240 can be composed of a plurality of
members. As shown in FIG. 6, the housing 240 is formed 5 by joining the front
housing 220 that covers the front side of the driver unit 210, the rear housing 230 that
covers the rear side of the driver unit 210, and the cable housing 290 that covers the
cable 291.
[0062]
10 Openings 221 and 222 which spatially connect the inside and the outside of
the housing 240 are provided in a partition wall of the front housing 220. The
openings 221 and 222 each correspond to the openings 121 and 122 shown in FIG. 1.
The opening 221 is an opening through which sounds are output to the outside, and is
provided inside the sound guiding tube 224 described above.
15 [0063]
An equalizer 227 which is a ventilation resistor is provided inside the sound
guiding tube 224. By appropriately setting a material and a shape of the equalizer
227, adjustment of sound quality, for example, reducing a component of a specific
frequency band for an output sound or the like, can be performed.
20 [0064]
The opening 222 is provided with a ventilation resistor 223 that plugs the
hole. The ventilation resistor 223 corresponds to the ventilation resistor 123 shown
in FIG. 1. Thus, a material and a shape of the ventilation resistor 223 of the
headphone 20 are also selected to substantially block air, as for the headphone 10.
25 As described above, in the present embodiment, the front air chamber 225 may be an
air-tightened air chamber that is spatially blocked from the outside except for the
opening 221. A resistive component of the ventilation resistor 223 to a flow of air
corresponds to resistance Rl in the acoustic equivalent circuit 40.
[0065]
30 The acoustic tube 250 that is configured by a tubular member and spatially
connects the rear air chamber 232 and an inner space 292 of the cable housing 290
28
through a tube is provided in a partial region of a partition wall of the rear housing
230. The acoustic tube 250 corresponds to the acoustic tube 150 shown in FIG. 1.
In the example shown in FIG. 6, an opening which spatially connects the rear air
chamber 232 and the outside of the housing 240 is provided in a partial region of a
partition wall of the housing 240 constituting the rear air chamber 5 232, and the
acoustic tube 250 is configured such that a tubular member thereof is connected to
the opening. Specifically, the acoustic tube 250 is provided to pass through the
opening that is provided in the partition wall of the rear housing 230 such that one
end of the acoustic tube is positioned in the rear air chamber 232 and the other end is
10 positioned in the inner space 292. A configuration of the acoustic tube 250,
however, is not limited thereto, and the tubular member may not be provided to, for
example, pass through the opening, and the acoustic tube 250 may have one end of
the tubular member connected to the opening.
[0066]
15 Here, in the present embodiment, the inner space 292 of the cable housing
290 is connected to the outside of the housing 240 (i.e., the outside of the headphone
20) with no substantial resistance to a flow of air. Thus, the acoustic tube 250 can
be said to connect the rear air chamber 232 and the outside of the housing 240 (i.e.,
the outside of the headphone 20) through the tube. Note that, in order to realize
20 such a configuration in the present embodiment, for example, an opening having a
size in which no substantial resistance to a flow of air is generated may be provided
in the partition wall of the cable housing 290, or the joining part of the rear housing
230 and the cable housing 290 may be joined in a simple method without taking air
tightness into consideration.
25 [0067]
The acoustic tube 250 is formed to have a length and an inner crosssectional
area in which a predetermined inductance component can be obtained with
respect to a flow of air passing through the inside of the acoustic tube 250. The
inductance component of the acoustic tube 250 with respect to a flow of air functions
30 as inductance Mb that acts on an acoustic characteristic in the acoustic equivalent
circuit 40. Note that a detailed configuration and shape of the acoustic tube 250
29
will be described in more detail in (4. Acoustic tube design method) below.
[0068]
In addition, in the present embodiment, an opening that spatially connects
the rear air chamber 232 and the inner space 292 or the outside of the housing 240
may not be provided in the region of the partition wall of the rear 5 housing 230 other
than the region in which the acoustic tube 250 is provided. Thus, the rear air
chamber 232 can be spatially blocked from the outside except for ventilation in the
acoustic tube 250. In order to realize such a configuration, the joining part of the
front housing 220 and the rear housing 230 is joined in a state in which, for example,
10 air tightness is maintained using an adhesive or the like. In addition, with regard to
the opening provided in the partition wall of the rear housing 230 to which the
acoustic tube 250 is connected, the joining part of the opening and the acoustic tube
250 is joined in a state in which, for example, air tightness is maintained using an
adhesive or the like. Note that the influence caused by providing an opening other
15 than the acoustic tube 250 in the partition wall of the rear housing 230 (which
corresponds to providing housing resistance to be described below) on the acoustic
characteristics of the headphone 20 will be described in detail in (3. Acoustic
characteristics of the headphone according to the present embodiment) below.
[0069]
20 In addition, although the acoustic tube 250 is formed such that the tubular
member is prepared separately from the housing 240 and the tubular member and the
housing 240 are combined in the example shown in FIG. 6, the embodiment is not
limited thereto. For example, the acoustic tube 250 may be formed integrated with
the housing 240. If the acoustic tube 250 is formed integrated with the housing 240,
25 it is not necessary to form an opening to be connected to the tubular member in the
partition wall of the housing 240, and thus air tightness of the rear air chamber 232
can be secured more reliably.
[0070]
One end of the acoustic tube 250 is provided in the inner space 292 of the
30 cable housing 290, and the cable 291 for audio signal transfer is drawn thereinto.
Specifically, although not illustrated in FIG. 6, the cable 291 that extends from
30
acoustic equipment that outputs audio signals is connected to the driver unit 210 via
the inner space 292 of the cable housing 290.
[0071]
A configuration of the inner space 292 of the cable housing 290 will be
described in detail with reference to FIG. 7. Referring to 5 FIG. 7, not only the
acoustic tube 250 but also a locking member 293 that locks the cable 291 and a
stopper 294 that fixes the locking member 293 are provided in the inner space 292.
The cable 291 that extends from acoustic equipment that outputs audio signals is
locked by the locking member 293 in the inner space 292, and thus the extension
10 direction changes to the direction in which the driver unit 210 is provided. In
addition, as the position of the locking member 293 is fixed by the stopper 294, a
position in which the cable 291 is disposed is fixed in the inner space 292. As
shown in FIG. 7, an opening 295 that guides the cable 291 into the rear air chamber
232 is provided in the partition wall of the rear housing 230 that is a partition wall
15 facing the inner space 292, and the cable 291 is inserted into the opening 295, is
extended to the inside of rear air chamber 232, and then is connected to the driver
unit 210. In the present embodiment, however, since the rear air chamber 232 can
be spatially blocked from the outside except for ventilation through the acoustic tube
250 as described above, the opening 295 may be plugged in a state in which, for
20 example, air tightness is maintained using a resin material or the like after the cable
291 is inserted thereinto.
[0072]
Here, a shape (a length and/or an inner cross-sectional area) of the acoustic
tube 250 of the headphone 20 according to the present embodiment and the way in
25 which the cable 291 is drawn into the inner space 292 of the cable housing 290 are
not limited to the example shown in FIG. 7, and may be appropriately changed
according to, for example, an acoustic characteristic of the headphone 20, the
disposition of members in the inner space 292, and the like. Several modified
examples of the headphone 20 according to the present embodiment will be
30 described with reference to FIGS. 8A to 8C.
[0073]
31
Since an acoustic characteristic is adjusted by changing a value of the
inductance Mb of the acoustic equivalent circuit 40 in the present embodiment as
described above, the shape (length and/or the inner cross-sectional area) of the
acoustic tube 250 can be appropriately changed. A modified example of the
headphone 20 according to the present embodiment in which 5 the shape of the
acoustic tube 250 is changed will be described with reference to FIG. 8A. FIG. 8A
is an exploded perspective diagram showing a configuration of the modified example
of the headphone 20 according to the present embodiment in which the shape of the
acoustic tube 250 is changed. Note that a headphone 20a according to the present
10 modified example corresponds to one obtained by changing the size of the inner
diameter of the acoustic tube 250 of the headphone 20 of the present embodiment
described above, and other configurations thereof may be the same as those of the
headphone 20. In addition, FIG. 8A is an exploded perspective diagram that
corresponds to FIG. 7, showing exploded external appearance of one portion of a
15 cable housing 290 of the headphone 20a according to the present modified example,
and the disposition of an acoustic tube 250a and a cable 291 to be described below
within the cable housing 290 is illustrated.
[0074]
Referring to FIG. 8A, the acoustic tube 250a provided in the headphone 20a
20 according to the present modified example is formed to have a larger inner diameter
than that of the acoustic tube 250 provided in the headphone 20 shown in FIG. 7.
The acoustic tube 250a having the larger inner diameter as shown in FIG. 8A is easy
to form to be integrated with a housing 240. The housing 240 can be formed using
a method, for example, an injection molding method or the like, and if the inner
25 diameter of the acoustic tube 250a is relatively large, a desired inner diameter is easy
to secure when it is formed to be integrated with the housing 240. By forming the
acoustic tube 250a to be integrated with the housing 240 as described above, air
tightness of the rear air chamber 232 can be reliably secured, and thus if the inner
diameter of the acoustic tube 250a is relatively large, it is preferable that the acoustic
30 tube 250a be formed to be integrated with the housing 240.
[0075]
32
In addition, FIGS. 8B and 8C are exploded perspective diagrams showing
configurations of modified examples of the headphone 20 of the present embodiment
in which the way of drawing a cable 291 into an inner space 292 of the cable housing
290 is changed. Referring to FIG. 8B, a headphone 20b according to the present
modified example corresponds to one obtained by changing the 5 way of drawing the
cable 291 into the headphone 20 shown in FIG. 7 provided with the acoustic tube 250
having a relatively small inner diameter, and other configurations may be the same as
those of the headphone 20. In addition, FIG. 8B is an exploded perspective diagram
corresponding to FIG. 7, showing the external appearance of the headphone 20b
10 according to the present modified example in which a portion of a cable housing 290
is exploded, and the disposition of an acoustic tube 250 and a cable 291 in the cable
housing 290 is illustrated.
[0076]
As shown in FIG. 8B, in the headphone 20b according to the present
15 modified example, the cable 291 that extends from audio equipment that outputs
audio signals is drawn out between a locking member 293 and a stopper 294. Then,
the cable 291 is inserted into an opening 295 that is provided in a partition wall of a
rear housing 230 that is a partition wall facing an inner space 292, is extended to the
inside of a rear air chamber 232, and is connected to a driver unit 210. As shown in
20 FIG. 8B, the stopper 294 can fix both the locking member 293 and the cable 291 in
the present modified example. By appropriately changing the configuration of the
locking member 293 and the stopper 294 in the present embodiment as described
above, the way in which the cable 291 is drawn may be appropriately changed.
[0077]
25 In addition, FIG. 8C illustrates a configuration example of a modified
example in which a way of drawing a cable 291 is changed from that of the
headphone 20a provided with an acoustic tube 250a having a relatively large inner
diameter shown in FIG. 8A. FIG. 8C is an exploded perspective diagram
corresponding to FIG. 8A, showing the external appearance of a headphone 20c
30 according to the present modified example in which a portion of a cable housing 290
is exploded, and the disposition of the acoustic tube 250a and the cable 291 in the
33
cable housing 290 is illustrated.
[0078]
Referring to FIG. 8C, the cable 291 that extends from acoustic equipment
that outputs audio signals is drawn from a gap between a locking member 293 and a
stopper 294 in the headphone 20c according to the present modified 5 example, like
the headphone 20b shown in FIG. 8B described above. In this manner, the stopper
294 can also fix both a locking member 293 and the cable 291 in the present
modified example. In the present modified example, however, an opening 295 is
not provided in a partition wall of a rear housing 230, and the cable 291 is inserted
10 into the tube of the acoustic tube 250a, is extended to the inside of a rear air chamber
232, and is connected to a driver unit 210.
[0079]
If the inner diameter of the acoustic tube 250a is relatively large as in the
present modified example, the cable 291 may be inserted thereinto and the cable 291
15 may be extended to the inside of the rear air chamber 232. In this case, the opening
295 may not be provided as shown in FIG. 8C. Without providing the opening 295,
it is not necessary to consider air tightness of the opening 295, and thus air tightness
in the rear air chamber 232 is maintained more reliably. Note that, if the inner
diameter of the acoustic tube 250a is relatively large and even if the cable 291 is
20 inserted thereinto, the inside of the acoustic tube 250a will not be plugged with the
cable 291, and thus the function of the acoustic tube 250a relating to acoustic
characteristics will not be impaired. In addition, by appropriately calculating, for
example, an inductance component Mb and a resistive component of the acoustic
tube 250a when taking the influence caused by the insertion of the cable 291 into
25 consideration, acoustic characteristics of the headphone 20c can be evaluated using
the acoustic equivalent circuit 40 in the same manner as described above.
[0080]
The configuration of the headphone 20 according to the embodiment of the
present disclosure has been described with reference to FIGS. 4A to 4F, 5, 6, and 7.
30 In addition, with reference to FIGS. 8A to 8C, the modified examples of the
headphone 20 according to the present embodiment in which the shape of the
34
acoustic tube 250 and the way in which the cable 291 is drawn into the inner space
292 of the cable housing 290 are changed have been described.
[0081]
(3. Acoustic characteristics of the headphone according to the present embodiment)
Next, acoustic characteristics of the headphone 20 according 5 to the present
embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a graph
diagram showing sound pressure level characteristics of the headphone 20 according
to the present embodiment. FIG. 10 is a graph diagram for describing an effect of
the acoustic resistance Rd in the sound pressure level characteristics of the
10 headphone 20 according to the present embodiment. In FIGS. 9 and 10, the
horizontal axis represents frequency, the vertical axis represents sound pressure level,
and the sound pressure level characteristics of the headphone 20 obtained from the
analysis result of the acoustic equivalent circuit 40 shown in FIG. 2 are plotted. In
FIGS. 9 and 10, however, a plurality of curves indicating sound pressure level
15 characteristics that correspond to cases in which the configuration of the headphone
20 is changed are illustrated for comparison.
[0082]
Referring to FIG. 9, three curves indicating sound pressure level
characteristics are illustrated. The curve D indicated by a dotted line in the drawing
20 indicates the sound pressure level characteristic of the headphone 20 according to the
present embodiment having the configuration shown in FIGS. 4A to 4F, 5, 6, and 7.
In addition, the curve F indicated by a dashed line in the drawing indicates the sound
pressure level characteristic of the headphone 20 according to the present
embodiment when the acoustic tube 250 is not provided (in other words, when the
25 inductance Mb is not provided in the acoustic equivalent circuit 40). In addition,
the curve E indicated by a solid line in the drawing indicates the sound pressure level
characteristic of the headphone 20 according to the present embodiment when an
opening that leads to the outside of the housing 240 is provided in a partition wall of
the housing 240 that constitutes the rear air chamber 232, in addition to the acoustic
30 tube 250, and a ventilation resistor that acts as resistance to a flow of air is further
provided in the opening. The opening and the ventilation resistor act as a resistive
35
component in the acoustic equivalent circuit 40, and can change an acoustic
characteristic of the headphone 20. Since the ventilation resistor, which is a
ventilation resistor provided in the opening formed in the partition wall of the
housing 240 and is provided in the opening that spatially connects the rear air
chamber 232 and the outside of the housing 240, other than the acoustic 5 tube 250, is
a resistive component provided in the partition wall of the housing 240, it will also
be referred to as a housing resistance in the description below. In such a headphone
having the housing resistance, the rear air chamber 232 is spatially connected to the
outside of the housing 240 through at least two portions including the acoustic tube
10 250 and the opening in which the housing resistance is provided. In this manner,
the headphone corresponding to the curve F corresponds to one obtained by
removing the acoustic tube 250 from the configuration of the headphone 20
corresponding to the curve D, and the headphone corresponding to the curve E
corresponds to one obtained by adding the housing resistance to the configuration of
15 the headphone 20 corresponding to the curve D.
[0083]
The curve F can be said to correspond to the curve A described with
reference to FIG. 3, and to indicate the sound pressure level characteristic of an
existing general headphone. Referring to FIG. 9, the curve F has a characteristic in
20 which the sound pressure level gently decreases in the middle register. As
described with reference to FIG. 3, it is hard to say that the sound pressure level
characteristic indicated by the curve F is preferable for, for example, a voice of a
person.
[0084]
25 On the other hand, in the curve D indicating the characteristic of the
headphone 20 according to the present embodiment, the sound pressure level
decreases from the lower register to the middle register with a steeper slope than in
the curve F. It can be said that, in the curve D, the stair-like sound pressure level
characteristic that is one ideal acoustic characteristic is realized like that as illustrated
30 using the curve C in FIG. 3. It can be considered that the stair-like sound pressure
level characteristic is realized in the headphone 20 according to the present
36
embodiment as shown by the curve D because, by providing the acoustic tube 250,
anti-resonance caused by an acoustic inductance (inductance Mb caused by the
acoustic tube 250) and an acoustic capacity (capacitance Cb caused at least by the
rear air chamber 232) has occurred and thus a dip of the sound pressure level has
been formed in 5 the middle register.
[0085]
In order to realize a desired sound pressure level characteristic in the present
embodiment, the inner cross-sectional area and the length of the acoustic tube 250
and at least the volume of the rear air chamber 232 are adjusted, accordingly, values
10 of the inductance Mb and the capacitance Cb are adjusted, and thereby the position
of the dip (i.e., the position of a resonance frequency fh of anti-resonance) is
controlled. The position of the dip can also be controlled by further adjusting the
volume of driver unit rear air chamber. In the present embodiment, for example, the
inner cross-sectional area and the length of the acoustic tube 250 and the volumes of
15 the driver unit rear air chamber 218 and the rear air chamber 232 can be adjusted so
that the resonance frequency fh is about 350 (Hz) to 650 (Hz). Specifically, in the
example shown in FIG. 9, the curve D indicates the sound pressure level
characteristic of the headphone 20 when the total volume of the driver unit rear air
chamber 218 and the rear air chamber 232 is 400 (mm3) and the size of the acoustic
20 tube 250 has inner diameter=0.55 (mm) and length=8 (mm).
[0086]
In addition, as described in (2. Configuration of a headphone according to
the present embodiment) above, the headphone 20 according to the present
embodiment can be configured such that the rear air chamber 232 is spatially blocked
25 from the outside except for ventilation in the acoustic tube 250. In FIG. 9, the curve
E which indicates the sound pressure level characteristic of the headphone which
further has the housing resistance in addition to the acoustic tube 250 is also
illustrated for comparison. Comparing the curve E to the curve D, it can be seen
that, due to the provision of the housing resistance, the slope of the sound pressure
30 level becomes more gentle from the lower register to the middle register. In the
present embodiment as described above, if a housing resistance is not provided (in
37
other words, if the rear air chamber 232 is configured to be spatially blocked from
the outside except for ventilation in the acoustic tube 250), the sound pressure level
characteristic in which the sound pressure level decreases with a steeper slope can be
obtained.
5 [0087]
In addition, FIG. 10 illustrates the sound pressure level characteristic of the
headphone 20 according to the present embodiment when an acoustic resistance
(resistance Rd) that corresponds to the ventilation resistor 217 provided in the vent
hole 216 which spatially connects the driver unit rear air chamber 218 and the rear
10 air chamber 232 is not provided. The curve G indicated by a solid line in the
drawing indicates the sound pressure level characteristic of the headphone 20
according to the present embodiment when the ventilation resistor 217 is not
provided (in other words, when the resistance Rd is not provided). The curve G can
be said to correspond to the curve B described with reference to FIG. 3. In addition,
15 the curve H indicated by a dotted line in the drawing indicates the sound pressure
level characteristic of the headphone 20 according to the present embodiment when
neither the acoustic tube 250 nor the ventilation resistor 217 is provided (in other
words, when neither the inductance Rb nor the resistance Rd is provided). Like this,
the headphone corresponding to the curve G corresponds to one obtained by
20 removing the ventilation resistor 217 from the configuration of the headphone 20
corresponding to the curve D, and the headphone corresponding to the curve H
corresponds to one obtained by removing the acoustic tube 250 and the ventilation
resistor 217 from the configuration of the headphone 20 corresponding to the curve
D.
25 [0088]
Comparing the curve G to the curve H, it can be seen that, by providing the
acoustic tube 250 when the resistance Rd is not provided, a dip is formed in the
middle register. Referring to the curve G, however, while the dip is formed by
providing the acoustic tube 250, the sound pressure level radically increases in the
30 frequency band of about 500 (Hz) or higher, and thus it is hard to say that a sound
pressure level characteristic in which a change of the sound pressure level is
38
relatively small is obtained in the middle register. When the resistance Rd is not
provided as described above, it is difficult to obtain the stair-like sound pressure level
characteristic that is one ideal acoustic characteristic.
[0089]
On the other hand, by providing the resistance Rd in addition 5 to forming a
dip by providing the acoustic tube 250 in the present embodiment, a value of the
sound pressure level from the lower register to the middle register is adjusted.
Accordingly, it is possible to realize the sound pressure level characteristic, for
example, as indicated by the curve D shown in FIG. 9 in which the quality of a sound
10 of the middle register is more improved while a sound of a lower register is more
emphasized.
[0090]
Here, an acoustic characteristic of an existing headphone as described in, for
example, Patent Literature 1 will be reviewed. For example, the headphone
15 described in Patent Literature 1 is provided with a duct structure that is similar to the
acoustic tube 250 of the present embodiment.
[0091]
A front air chamber of the existing headphone, however, is not an airtightened
front air chamber, and thus a relatively high sound pressure level is not
20 maintained in the lower register. In addition, the headphone described in Patent
Literature 1 above is provided with such a housing resistance described above in a
rear air chamber. If the housing resistance is provided, the slope that indicates a
decrease of the sound pressure level from the lower register to the middle register
becomes gentle as described with reference to FIG. 9. Thus, the sound pressure
25 level characteristic of the headphone described in Patent Literature 1 is not
necessarily a preferable characteristic from the perspective of more improving the
quality of a sound of the middle register while more emphasizing a sound of the
lower register.
[0092]
30 On the other hand, in the present embodiment, it is possible to realize the
acoustic characteristic in which the sound pressure level in the lower register is
39
higher than the sound pressure level in the middle register, i.e., a sound of the lower
register is more emphasized by forming the air tightened front air chamber. In
addition, as described with reference to FIG. 9, as a housing resistance is not
provided in the present embodiment, the slope that indicates a decrease of the sound
pressure level from the lower register to the middle register 5 can be steeper.
[0093]
As described above, it is considered that, even if the configuration described
in Patent Literature 1 is applied without change, it is difficult to realize the acoustic
characteristic of the headphone 20 according to the present embodiment. It is
10 possible to say that, as the front air chamber is set to be air tightened and a housing
resistance is not provided in the rear housing 230 in the headphone 20 according to
the present embodiment, a desired sound pressure level characteristic in which the
quality of a sound of the middle register is more improved while a sound of the lower
register is more emphasized is realized.
15 [0094]
(4. Acoustic tube design method)
Next, a specific design method of the acoustic tube 250 and driver unit 210
according to the present embodiment will be described exemplifying the headphone
20. As described with reference to FIG. 3, by adjusting the value of the resonance
20 frequency fh of anti-resonance caused by the capacitance Cd, the capacitance Cb,
and the inductance Mb in the present embodiment, the acoustic characteristic of the
headphone 20 is improved. Here, the inductance Mb depends on the length and the
inner cross-sectional area of the acoustic tube 250, the capacitance Cb depends on
the volume of the rear air chamber 232 (i.e., the shape of the housing 240), and the
25 capacitance Cd depends on the volume of the driver unit rear air chamber 218 (i.e.,
the shape of the driver unit 210) as described above. As an example of the present
embodiment, a method of designing the length and the inner cross-sectional area of
the acoustic tube 250, and the volumes of the rear air chamber 232 and the driver unit
rear air chamber 218 which cause the resonance frequency fh of anti-resonance to be
30 included in the frequency band of 350 (Hz) to 650 (Hz) will be described below.
[0095]
40
Note that, as the ventilation resistor 217 provided between the rear air
chamber 232 and the driver unit rear air chamber 218, one having a relatively small
resistance to a flow of air (i.e., one having relatively small resistance Rd) can be
selected in the present embodiment as described in (2. Configuration of a headphone
according to the present embodiment) above. Thus, for the sake 5 of simplification in
description below, the combined capacitance of the capacitance Cb and the
capacitance Cd (i.e., the volume that corresponds to the total volume of the rear air
chamber 232 and the driver unit rear air chamber 218) is assumed to be Cs, and a
case in which anti-resonance occurs due to the inductance Mb and the capacitance Cs
10 will be described. When a more sophisticated analysis is to be performed, values of
Mb, the capacitance Cb, and the capacitance Cd that can impart the desired
resonance frequency fh can be obtained through calculation using, for example,
various circuit simulations and the like with respect to acoustic equivalent circuit 40
shown in FIG. 2.
15 [0096]
The resonance frequency fh (Hz) of anti-resonance caused by the inductance
Mb and the capacitance Cs is expressed by Expression (1) below.
[0097]
[Math. 1]
20
[0098]
In addition, the inductance Mb is expressed by Expression (2) below by
setting the length of the acoustic tube 250 to L (m) and the inner cross-sectional area
thereof to S (m2).
25 [0099]
[Math. 2]
41
[0100]
Here, ρ (kg/m3) represents air density. In addition, the capacitance Cs is
expressed by Expression (3) below by setting the volume of the driver unit rear air
chamber 218 and the rear air chamber 232 to V (m3). Note that 5 c (m/s) represents
sound velocity in air.
[0101]
[Math. 3]
10 [0102]
Using Expressions (1) to (3) described above, it is possible to obtain
conditions for the length L and the inner cross-sectional area S of the acoustic tube
250 and the volume V of the rear air chamber 232 and the driver unit rear air
chamber 218 that can cause, for example, the resonance frequency fh to be included
15 in the frequency band of 350 (Hz) to 650 (Hz). For example, the relations between
the resonance frequency fh and the length L of the acoustic tube 250 and the inner
cross-sectional area S of the acoustic tube 250 in the case of V=400 (mm3) are shown
in the following table. Note that, in the table below, as parameters indicating the
length L (mm) of the acoustic tube 250 and the inner cross-sectional area S (mm2) of
20 the acoustic tube 250, ratios L/S (1/mm2) of the length L (mm) of the acoustic tube
250 to the inner cross-sectional area S (mm2) thereof are calculated.
[0103]
[Table 1]
42
[0104]
Referring to the table above, it can be seen that the ratio L/S (1/mm) of the
length L (mm) of the acoustic tube 250 to the inner cross-sectional area S (mm2)
thereof is desirably 13 to 45 (１/mm) in order to cause the resonance 5 frequency fh to
be included in 350 (Hz) to 650 (Hz). In reality, for example, it may be possible that
several types of acoustic tubes 250 having different shapes are prepared and they can
be differently used according to applications. For example, it may be possible in
the present embodiment that an acoustic tube 250 having an inner diameter of 0.6
10 (mm) and a length of 8 (mm) and an acoustic tube 250 having an inner diameter of
1.2 (mm) and a length of 8 (mm) are produced and headphones 20 each provided
43
with the acoustic tubes 250 are produced as headphones 20 of different types.
[0105]
In the present embodiment, a shape (a length and an inner cross-sectional
area) of the acoustic tube 250, a shape of the housing 240, and a shape of the driver
unit 210 which causes the resonance frequency fh to be included 5 in a desired
frequency band, for example, 200 (Hz) to 400 (Hz), can be designed using
Expressions (1) to (3) as described above. In the example above, as an example of
a method for designing the acoustic tube 250, the housing 240, and the driver unit
210 according to the present embodiment, the method for designing the acoustic tube
10 250, the housing 240, and the driver unit 210 has been introduced under conditions in
which the resonance frequency fh is to be included in the range of 350 (Hz) to 650
(Hz) and the volume V of the rear air chamber 232 and the driver unit rear air
chamber 218 is to be 400 (mm3); however, the present embodiment is not limited
thereto. Even in cases of conditions in which the resonance frequency fh is to be
15 included in another frequency band and the volume V of the rear air chamber 232
and the driver unit rear air chamber 218 is to have another value, the acoustic tube
250, the housing 240, and the driver unit 210 can be designed using the same method
as described above.
[0106]
20 Note that, when values of a length L (mm) and an inner cross-sectional area
S (mm2) of the acoustic tube 250 are designed, processing accuracy in manufacturing
the acoustic tube 250 may be considered. For example, minimum values of a length
L (mm) and an inner cross-sectional area S (mm2) may be limited to values at which
the acoustic tube 250 can be manufactured within a predetermined dimensional
25 tolerance. In addition, a shape of the driver unit 210 can directly affect an acoustic
characteristic of sounds generated by the driver unit 210. Thus, when the driver
unit 210 is designed, the acoustic characteristic of sounds generated by the driver
unit 210 may be considered. In addition, when a shape of the housing 240 is
designed, elements other than an acoustic characteristic, for example, user
30 wearability of the headphone 20 and designability thereof may be considered. In
the case of a canal earphone as exemplified in FIG. 6, for example, a size of the
44
housing 240 is set to be relatively small, and in the case of so-called overhead
headphones, for example, a size of the housing 240 is set to be larger. In this
manner, a shape of the housing 240 may be designed comprehensively in
consideration of wearability, designability, and the like of the headphone 20, in
addition to the acoustic 5 characteristic.
[0107]
(5. Modified example)
According to the present embodiment, the headphone having the acoustic
characteristic in which the quality of a sound of the middle register is more improved
10 while a sound of the lower register is more emphasized is realized as described above.
However, there is a desire to more freely adjust an acoustic characteristic of the same
headphone according to preference of a user or a peripheral situation.
[0108]
Generally, there are headphones with a relatively large housing that houses a
15 driver unit, such as so-called overhead headphones, which are provided with a
mechanism for adjusting an acoustic characteristic (hereinafter referred to as an
acoustic characteristic adjustment mechanism). However, since a size of a housing
is small in a so-called inner-ear headphone such as a canal earphone, it is difficult to
provide an acoustic characteristic adjustment mechanism, and thus there are few
20 products that have the acoustic characteristic adjustment mechanism.
[0109]
In rare cases, there are inner-ear headphones provided with an acoustic
characteristic adjustment mechanism. In order to adjust an acoustic characteristic in
such an acoustic characteristic adjustment mechanism, however, a relatively
25 cumbersome operation, for example, rotating a screw or replacing a component using
a dedicated tool such as a screwdriver is necessary.
[0110]
Taking the above-described circumstances into consideration, a technology
for enabling an acoustic characteristic to be adjusted more easily even in a
30 headphone with a relatively small size of a housing such as an inner-ear headphone
has been demanded. Thus, as a result of discussing a technology for enabling an
45
acoustic characteristic to be adjusted more easily, the present inventors think that an
acoustic characteristic adjustment mechanism that enables an acoustic characteristic
to be adjusted through a relatively simple operation can be realized using the
headphone according to the embodiment described above.
5 [0111]
As a modified example of the present embodiment, a modified example in
which an acoustic characteristic adjustment mechanism with which an acoustic
characteristic can be adjusted through a simpler operation is added to the
embodiment described above will be described below. Note that a headphone
10 according to the present modified example to be described below is one in which the
acoustic characteristic adjustment mechanism to be described below is added to the
headphone of the embodiment described above, and other configurations thereof may
be substantially the same as the headphone of the embodiment described above.
Thus, in the description with regard to the present modified example below, the
15 detailed description regarding the configurations described above will be omitted,
and different configurations from the embodiment above will be mainly described.
[0112]
In addition, with respect to the headphone according to the present modified
example, it is possible to generate an acoustic equivalent circuit that represents
20 characteristics of the headphone according to the present modified example by
replacing configurations with electric elements, as in the acoustic equivalent circuit
40 shown in FIG. 2. The acoustic equivalent circuit of the headphone according to
the present modified example can be one obtained by changing some elements of the
acoustic equivalent circuit 40 shown in FIG. 2 corresponding to the constituent
25 members that are newly added in the present modified example. Thus, as in FIGS.
1 and 6, reference symbols of the elements of the acoustic equivalent circuit 40 are
affixed to several reference numbers given to the constituent members of the
headphone according to the present modified example.
[0113]
30 (5-1. Configuration of the headphone according to the present modified example)
A configuration of the headphone according to a modified example of the
46
present embodiment will be described with reference to FIGS. 11A to 15. FIGS.
11A to 11F are hexahedral diagrams showing the external appearance of the
headphone according to a modified example of the present embodiment. FIGS.
12A and 12B are cross-sectional diagrams of one cross-section of the headphone
according to the present modified example. FIGS. 13A and 13B 5 are cross-sectional
diagrams of another cross-section of the headphone according to the present
modified example. FIG. 14 is a cross-sectional diagram of still another crosssection
of the headphone according to the present modified example. FIG. 15 is a
perspective diagram showing a configuration of a switch member mounted in the
10 headphone according to the present modified example.
[0114]
Note that FIGS. 12A and 12B are the cross-sectional diagrams of the crosssection
of the headphone according to the present modified example, which is
parallel with the y-z plane, and is obtained by cutting an acoustic tube 350 to be
15 described below in a longitudinal direction. In addition, FIGS. 13A and 13B are the
cross-sectional diagrams of the cross-section of the headphone according to the
present modified example, which is parallel with the x-z plane, and is obtained by
cutting the acoustic tube 350 to be described below in a longitudinal direction. In
addition, FIG. 14 is the cross-sectional diagram of the cross-section of the headphone
20 according to the present modified example, which is parallel with the x-y plane and
is obtained by cutting the acoustic tube 350 to be described below in a radial
direction.
[0115]
In addition, as will be described below, the switch member shown in FIG. 15
25 constitutes an acoustic characteristic adjustment mechanism, and when the switch
member is operated, an acoustic characteristic is adjusted in the present modified
example. FIGS. 12A and 12B illustrate states of the headphone before and after the
switch member is moved. Likewise, FIGS. 13A and 13B also illustrate states of the
headphone before and after the switch member is moved.
30 [0116]
Referring to FIGS. 11A to 14, a headphone 30 according to the present
47
modified example is provided with a driver unit 310, a housing 340 that houses the
driver unit 310, and an acoustic characteristic adjustment mechanism 360. Note
that the headphone 30 illustrated in FIGS. 11A to 14 is simplified for description of
the present modified example, and the headphone 30 may be further provided with
constituent members that are not illustrated. Since the constituent 5 members that are
not illustrated can be those known as configurations of existing general headphones,
detailed description thereof will be omitted.
[0117]
The driver unit 310 has a frame 311, a vibration plate 312, a magnet 313, a
10 plate 314, and a voice coil 315. The driver unit 310 corresponds to the driver units
110 and 210 shown in FIGS. 1 and 6. In addition, the frame 311, the vibration plate
312, the magnet 313, the plate 314, and the voice coil 315 each correspond to the
frames 111 and 211, the vibration plates 112 and 212, the magnets 113 and 213, the
plates 114 and 214, and the voice coils 115 and 215 shown in FIGS. 1 and 6.
15 [0118]
A driver unit rear air chamber 318 is formed between the frame 311 and the
vibration plate 312. An element that corresponds to vibratory force generated when
the vibration plate 312 vibrates corresponds to a signal source (electromotive force)
Vs of the acoustic equivalent circuit 40. In addition, a mass, mechanical resistance,
20 and compliance of the driver unit 310 respectively correspond to inductance Mo,
resistance Ro, and capacitance Co of the acoustic equivalent circuit 40.
Furthermore, a capacity of the driver unit rear air chamber 318 corresponds to the
capacitance Cd of the acoustic equivalent circuit 40.
[0119]
25 As shown in FIGS. 12A and 12B, a vent hole 316 that passes through the
frame 311 in the z axis direction is provided in the frame 311 of the driver unit 310.
The vent hole 316 corresponds to the vent holes 116 and 216 shown in FIGS. 1 and 6.
The vent hole 316 is provided substantially at the center of the frame 311, and
spatially connects the driver unit rear air chamber 318 and the space which is a space
30 on the rear side of the driver unit 310 and is surrounded by the driver unit 310 and
the housing 340 (a rear air chamber 332 to be described below).
48
[0120]
The vent hole 316 is provided with a ventilation resistor 317 that plugs the
hole. The ventilation resistor 317 corresponds to the ventilation resistors 117 and
217 shown in FIGS. 1 and 6. A resistive component of the ventilation resistor 317
to a flow of air corresponds to resistance Rd in the acoustic equivalent 5 circuit 40.
[0121]
Here, a material and a shape of the ventilation resistor 317 may be
appropriately set so that a desired sound pressure level characteristic is obtained in
consideration of, for example, the sound pressure level characteristic shown in FIG. 3.
10 More specifically, as described with reference to FIG. 3, a material and a shape of the
ventilation resistor 317 can be appropriately set so that a value of the resistance Rd
with which the stair-like sound pressure level characteristic is obtained is realized.
In this manner, a characteristic relating to a ventilation resistance such as a material
of the ventilation resistor 317 can be appropriately selected in consideration of the
15 influence of the resistance Rd on the acoustic characteristic of the headphone 30. In
addition, since the configuration and the function of the ventilation resistor 317 are
the same as those of the ventilation resistors 117 and 217 described above, detailed
description thereof will be omitted.
[0122]
20 Note that, like the vent hole 216 described with reference to FIG. 6, a
formation position of the vent hole 316 and the number thereof to be formed are not
limited to the example shown in FIGS. 12A and 12B in the present modified example.
A position in the frame 311 at which the vent hole 316 is provided may be a position
at which the ventilation resistor 317 provided in the vent hole 316 has the same
25 function as in the acoustic equivalent circuit 40, and may be appropriately set in
consideration of, for example, disposition positions of other constituent members in
the housing 340.
[0123]
The housing 340 corresponds to the housings 140 and 240 shown in FIGS. 1
30 and 6. A front air chamber 325 which is a space surrounded by the driver unit 310
and the housing 340 is formed on the front side of the driver unit 310. In addition,
49
the rear air chamber 332 which is a space surrounded by the driver unit 310 and the
housing 340 is formed on the rear side of the driver unit 310. The volume of the
front air chamber 325 and the volume of the rear air chamber 332 respectively
correspond to capacitance Cl and capacitance Cb in the acoustic equivalent circuit 40.
5 [0124]
The housing 340 can be composed of a plurality of members. As shown in
FIGS. 11A to 13B, the housing 340 is formed by joining the front housing 320 that
covers the front side of the driver unit 310, the rear housing 330 that covers the rear
side of the driver unit 310, and the cable housing 390 that covers the cable 391.
10 [0125]
A sound guiding tube 324 that is a tubular portion protruding toward the
outside is formed in a partial region of the front housing 320. The sound guiding
tube 324 corresponds to the sound guiding tubes 124 and 224 shown in FIGS. 1 and
6. In addition, an earpiece 326 for bringing the sound guiding tube 324 in close
15 contact with the inner wall of an external auditory canal of a user is provided in the
outer circumference of a tip of the sound guiding tube 324. An opening for sound
output (an opening 321 shown in FIGS. 13A and 13B) is provided inside the sound
guiding tube 324, and when a user listens to a sound, the tip of the sound guiding
tube 324 including the earpiece 326 is inserted into the external auditory canal of the
20 user as shown in FIG. 5. As described above, the headphone 30 according to the
present modified example may be the so-called canal earphone.
[0126]
An equalizer 327 which is a ventilation resistor is provided inside the sound
guiding tube 324. By appropriately setting a material and a shape of the equalizer
25 327, adjustment of sound quality, for example, reducing a component of a specific
frequency band for an output sound or the like, can be performed.
[0127]
Openings 321 and 322 that spatially connect the inside and the outside of
the housing 340 are provided in the partition wall of the front housing 320. The
30 openings 321 and 322 correspond to the openings 121 and 221, and the openings 122
and 222 shown in FIGS. 1 and 6. The opening 321 is an opening for outputting
50
sounds to the outside, and is provided at the position corresponding to the sound
guiding tube 324 as described above.
[0128]
The opening 322 is provided with a ventilation resistor 323 to plug the hole.
The ventilation resistor 323 corresponds to the ventilation resistors 5 123 and 223
shown in FIGS. 1 and 6. Like the ventilation resistors 123 and 223, a material and a
shape of the ventilation resistor 323 are selected to substantially block air. In the
present modified example, the front air chamber 325 may be an air-tightened air
chamber that is spatially blocked from the outside except for the opening 321 as
10 described. A resistive component of the ventilation resistor 323 to a flow of air
corresponds to the resistance Rl of the acoustic equivalent circuit 40.
[0129]
Openings 333 and 351 that spatially connect the rear air chamber 332 and an
inner space 392 of the cable housing 390 are provided in partial regions of the
15 partition wall of the rear housing 330. The opening 333 is an opening for inserting
the cable 391 thereinto. The cable 391 that extends from acoustic equipment (not
illustrated) that outputs audio signals is connected to the driver unit 310, passing
through the inner space 392 of the cable housing 390 via the opening 333. Note
that, in FIGS. 12A and 12B, the state of the cable 391 inserted into the opening 333
20 is not illustrated to avoid the drawing becoming more complicated.
[0130]
Although the opening 333 is illustrated as spatially connecting the rear air
chamber 332 and the inner space 392 in FIGS. 12A and 12B, actually, after the cable
391 is inserted into the opening 333, the remaining space of the opening 333 is
25 plugged with an arbitrary sealing material which maintains air tightness. In this
manner, in the headphone 30, only the opening 351 spatially connects the rear air
chamber 332 and the inner space 392 of the cable housing 390.
[0131]
A tubular part 354 that projects toward the inner space 392 of the cable
30 housing 390 in a tubular shape is provided along the edge of the opening 351. The
tubular part 354 is formed to have a cylindrical shape. The tubular part 354
51
constitutes at least a partial side wall of the acoustic tube 350 that spatially connects
the rear air chamber 332 and the inner space 392 through the tube, and the opening
351 can constitute a hollow part of the acoustic tube 350.
[0132]
A packing 352 in a hollow cylindrical shape 5 is fitted to the outer
circumferential part of the tubular part 354. The inner diameter of the packing 352
is formed to correspond to the outer diameter of the cylindrical tubular part 354, and
both are fitted with air tightness maintained. As shown in FIGS. 12A to 13B, one
end of the packing 352 having a cylindrical shape is fitted to the tubular part 354, and
10 the other end of the packing 352 extends toward the inner space 392. Since the
fitted portion of the tubular part 354 and the packing 352 maintains air tightness as
described above, the tubular part 354 and the packing 352 can function as a single
tube. In this manner, the acoustic tube 350 can be configured by the tubular part
354 and the packing 352 in the present modified example. The acoustic tube 350
15 corresponds to the acoustic tubes 150 and 250 shown in FIG. 1 and FIG. 6.
[0133]
The acoustic tube 350 is formed to have a length and an inner crosssectional
area in which a predetermined inductance component can be obtained with
respect to a flow of air passing through the inside of the acoustic tube 350. The
20 inductance component of the acoustic tube 350 with respect to a flow of air functions
as inductance Mb that acts on an acoustic characteristic in the acoustic equivalent
circuit 40.
[0134]
A length and an inner cross-sectional area of the acoustic tube 350 may be
25 appropriately set so that a desired sound pressure level characteristic is obtained in
consideration of, for example, the sound pressure level characteristic shown in FIG. 3.
Specifically, as described with reference to FIG. 3, the length and the inner crosssectional
area of the acoustic tube 350 can be appropriately set so that a value of the
inductance Mb that causes a resonance frequency at which anti-resonance occurs to
30 be positioned in a desired frequency band is realized. For example, a shape of the
acoustic tube 350 may be designed according to the technique described in (4.
52
Acoustic tube design method) above. By providing the acoustic tube 350 designed
above, the headphone30 can realize, for example, the stair-like sound pressure level
characteristic as described with reference to FIG. 3, like the headphones 10 and 20 of
the embodiments described above.
5 [0135]
The packing 352 can be formed of any of various elastic materials that are
generally used for packing (sealing member), for example, natural rubber, synthetic
rubber, a resin material, and the like. Thus, the packing 352 can be an elastic body.
[0136]
10 Partial regions of the partition wall of the rear housing 330 are extended
toward the inner space 392 as shown in FIGS. 12A to 13B so that the regions come
in contact with the outer circumferential part of the packing 352. The contact face
of the outer circumferential part of the packing 352 and the extending portions is
welded using, for example, ultrasonic waves or the like. Accordingly, the packing
15 352 is reliably fixed to the partition wall of the rear housing 330, and thus air
tightness of the fitting part of the tubular part 354 and the packing 352 can be further
strengthened.
[0137]
A supporting member 353 having a ring shape is fitted to the outer
20 circumferential part of a portion of the packing 352 that extends toward the inner
space 392. The supporting member 353 is attached to the packing 352 to press the
packing 352 toward the tubular part 354 (in other words, in the forward direction of
the z axis in the drawing). Accordingly, the packing 352 can be more reliably fixed
to the partition wall of the rear housing 330, the tubular part 354 can come in close
25 contact with the packing 352, and air tightness in the fitting part of the tubular part
354 and the packing 352 can be further strengthened.
[0138]
Here, in the present modified example, the inner space 392 of the cable
housing 390 is connected to the outside of the housing 340 (i.e., the outside of the
30 headphone 30) with no substantial resistance to a flow of air. Thus, the acoustic
tube 350 can be said to connect the rear air chamber 332 and the outside of the
53
housing 340 (i.e., the outside of the headphone 20) through the tube. Note that, in
order to realize such a configuration in the present modified example, for example,
an opening having a size in which no substantial resistance to a flow of air is
generated may be provided in the partition wall of the cable housing 390, or the
joining part of the rear housing 330 and the cable housing 390 5 may be joined in a
simple method without taking air tightness into consideration.
[0139]
In addition, in the present modified example, since the opening 333 is
plugged after the cable 391 is inserted thereinto as described above, the rear air
10 chamber 332 is configured to be spatially blocked from the inner space 392 (i.e., the
outside of the headphone 30) except for ventilation in the acoustic tube 350. In
order to realize the configuration, the joining part of the front housing 320 and the
rear housing 330 are joined in a state in which, for example, air tightness is
maintained using an adhesive or the like.
15 [0140]
By providing the acoustic tube 350 in the headphone 30 according to the
present modified example as described above, the same stair-like sound pressure
level characteristic is realized as in the headphones 10 and 20 according to the
embodiments described above. In the headphone 30 according to the present
20 modified example, however, the acoustic characteristic adjustment mechanism 360
that adjusts an acoustic characteristic of the headphone 30 by changing a
characteristic of the acoustic tube 350 is further provided.
[0141]
The acoustic characteristic adjustment mechanism 360 is constituted by a
25 switch member 361. The switch member 361 is constituted by an operation part
362 having a substantial plate shape and a boss 363 that projects in the substantial
parallel direction with a plane of the plate shape of the operation part 362 and has a
substantially cylindrical shape as shown in FIG. 15.
[0142]
30 The switch member 361 is attached to the housing 340 such that the boss
363 is inserted into an opening 356 of the packing 352 (i.e., the opening 356 of the
54
acoustic tube 350) and the operation part 362 is positioned outside of the housing
340 as shown in FIGS. 12A to 14. In addition, in this state, the switch member 361
is attached to the housing 340 to be movable in parallel with the projection direction
of the boss 363 (the z axis direction in the drawing). In other words, the boss 363 is
inserted into and removed from the opening 356 of the packing 5 352 through parallel
movements of the switch member 361.
[0143]
Here, a projecting part 364 that projects in the radial direction is provided in
a partial region of the boss 363 in the longitudinal direction as shown in FIGS. 12A
10 to 15. In addition, the boss 363 and the projecting part 364 are configured such that
the outer diameter of the boss 363 is smaller than the inner diameter of the packing
352 and the outer diameter of the projecting part 364 is greater than the inner
diameter of the packing 352.
[0144]
15 By forming the outer diameter of the boss 363, the outer diameter of the
projecting part 364, and the inner diameter of the packing 352 so as to satisfy the
above size relation, when the boss 363 is inserted into the opening 356 of the packing
352, the projecting part 364 of the boss 363 is press-fitted into the opening 356 of the
packing 352 that is an elastic body. Thus, the projecting part 364 comes in
20 pressured contact with the entire circumference of the inner wall of the opening 356
of the packing 352, and thus the opening 356 is plugged to more reliably prevent
ventilation in the opening 356.
[0145]
Here, a length of the boss 363 is adjusted in the present modified example
25 such that, when the boss 363 is pulled out from the opening 356 of the packing 352,
the boss 363 is not completely pulled out from the opening 356 of the packing 352
and a tip of the boss 363 is slightly positioned inside the opening 356 of the packing
352 (see FIGS. 12B and 13B). In addition, a formation position of the projecting
part 364 in the longitudinal direction of the boss 363 is adjusted such that, when the
30 boss 363 is pulled out from the opening 356 of the packing 352, at least the
projecting part 364 is pulled out from the opening 356 of the packing 352. In other
55
words, when the boss 363 is pulled out from the opening 356 of the packing 352
while the tip of the boss 363 is positioned inside the opening 356 of the packing 352,
the projecting part 364 of the boss 363 is not press-fitted into the opening 356 of the
packing 352 that is an elastic body, and thus ventilation in the opening 356 of the
packing 5 352 is maintained.
[0146]
Note that, notches are formed on side faces of the boss 363 that has a pillar
shape in the longitudinal direction of the pillar as shown in FIGS. 14 and 15. Thus,
when the boss 363 is pulled out from the opening 356 of the packing 352, even in the
10 state in which the tip of the boss 363 is slightly inserted into the opening 356 of the
packing 352, ventilation in the opening 356 of the packing 352 can be maintained
due to the notches at substantially the same degree as when there is not the switch
member 361.
[0147]
15 A user can, for example, operate the switch member 361 to move it in the z
axis direction with his or her finger pressing the upper face of the operation part 362.
With this operation, an insertion length of the boss 363 into the opening 356 of the
packing 352 is adjusted. FIGS. 12A and 13A illustrate a state in which the switch
member 361 moves in the forward direction of the z axis, the boss 363 is inserted
20 into the opening 356 of the packing 352, the opening 356 is plugged by the
projecting part 364, and thus ventilation is not performed in the acoustic tube 350
(hereinafter, this state will also be referred to as a closed state). In addition, FIGS.
12B and 13B illustrate a state in which the switch member 361 moves in the
backward direction of the z axis, the projecting part 364 of the boss 363 is pulled out
25 from the opening 356 of the packing 352, and thus ventilation in the acoustic tube
350 is ensured (hereinafter, this state will also be referred to as an open state).
[0148]
In the open state, ventilation in the acoustic tube 350 is ensured, and thus
the acoustic tube 350 has the same characteristics as those of the acoustic tubes 150
30 and 250 of the above-described embodiments. Thus, in the open state, the same
stair-like sound pressure level characteristic is realized in the headphone 30 as in the
56
above-described embodiments.
[0149]
On the other hand, in the closed state, ventilation in the acoustic tube 350 is
obstructed. Thus, the acoustic tube 350 does not function as a tube that spatially
connects the rear air chamber 332 and the inner space 392, and 5 thus the headphone
30 has a different acoustic characteristic from the stair-like sound pressure level
characteristic. Specifically, as ventilation in the acoustic tube 350 is not ensured,
operations of the vibration plate 312 of the driver unit 310 are suppressed, and a
sound pressure level in a lower register drastically decreases more than when
10 ventilation occurs. Note that a difference in acoustic characteristics in the open
state and the closed state will be described in detail in (5-2. Acoustic characteristic of
a headphone according to the present modified example) below.
[0150]
As described above, in the present modified example, the acoustic
15 characteristic adjustment mechanism 360 has the function of adjusting an acoustic
characteristic of the headphone 30 by changing the ventilation in the acoustic tube
350. Specifically, as the boss 363 of the switch member 361 is inserted into and
removed from the opening 356 of the packing 352 (i.e., the opening 356 of the
acoustic tube 350), the ventilation in the acoustic tube 350 is adjusted, and thus the
20 acoustic characteristic of the headphone 30 is adjusted. In addition, with the
configuration in which the projecting part 364 of the boss 363 is press-fitted into the
packing 352 that is an elastic body, it is possible to switch the state in which
ventilation in the acoustic tube 350 is ensured (the open state) and the state in which
ventilation is not performed (the closed state) more reliably.
25 [0151]
Here, in the present modified example, a length of the boss 363 is adjusted
as described above so that the tip of the boss 363 is slightly positioned in the opening
356 of the packing 352 even in the open state. This is because, if the tip of the boss
363 is completely pulled from the opening 356 of the packing 352 in the open state,
30 there is a possibility that, when a user next attempts to operate the switch member
361 and insert the boss 363 into the opening 356, the tip of the boss 363, for example,
57
comes in contact with an edge of the opening 356 or the like and thus a smooth
insertion is obstructed. When smooth insertion is not performed, there is concern of
user operability deteriorating. In the present modified example, by adjusting the
length of the boss 363 to the extent that the boss 363 is not completely removed from
the opening 356 of the packing 352 even in the open state, the 5 smooth insertion of
the boss 363 into the opening 356 becomes possible and thus user operability can be
improved.
[0152]
In addition, a projecting part 355 that projects in a radial direction is
10 provided in a partial region on the inner wall of the opening 356 of the packing 352
in the longitudinal direction as shown in FIGS. 12A to 15. The projecting part 355
is appropriately provided at a tip of the opening 356 of the packing 352 on the side
on which the boss 363 of the switch member 361 is inserted. Accordingly, in the
course of transition from the open state to the closed state and the course of transition
15 from the closed state to the open state, the projecting part 364 of the boss 363 moves
as if sliding over the projecting part 355 of the opening 356 of the packing 352, in
other words, the projecting part 364 of the boss 363 and the projecting part 355 of the
opening 356 of the packing 352 are engaged and rub against each other.
[0153]
20 Thus, when a user operates the switch member 361, the feeling given when
the projecting part 364 of the boss 363 passes over the projecting part 355 of the
opening 356 of the packing 352 is transferred to the user. Based on that feeling, the
user can sense the transition from the open state to the closed state and the transition
from the closed state to the open state, and thus can know a current state.
25 [0154]
The configuration of the headphone 30 according to a modified example of
the present embodiment has been described with reference to FIGS. 11A to 15. As
described above, the acoustic characteristic adjustment mechanism 360 that adjusts
the acoustic characteristic of the headphone 30 by changing the characteristic of the
30 acoustic tube 350 is provided in the present modified example. According to the
present modified example, by switching into the open state that is a state in which
58
ventilation in the acoustic tube 350 is ensured and the closed state in which
ventilation is not performed in the acoustic tube 350 with the acoustic characteristic
adjustment mechanism 360, the acoustic characteristic of the headphone 30 can be
adjusted.
5 [0155]
The acoustic characteristic adjustment mechanism 360 is constituted by, for
example, the switch member 361 that has the function of adjusting the ventilation in
the acoustic tube 350. The switch member 361 has a relatively simple
configuration in which the ventilation in the acoustic tube 350 is adjusted by
10 inserting or removing the boss 363 into or from the acoustic tube 350. In addition,
since the switch member 361 is moved manually by a user, another configuration for
driving the switch member 361 such as a power source is also unnecessary. In the
present modified example, by configuring the acoustic characteristic adjustment
mechanism 360 with such a relatively simple configuration like the switch member
15 361, the acoustic characteristic adjustment mechanism 360 can also be mounted in a
headphone having a housing of a relatively small size such as an inner-ear headphone.
[0156]
In addition, according to the present modified example, a user can adjust the
acoustic characteristic of the headphone 30 with a relatively simple operation of
20 sliding the switch member 361. In addition, the user can easily know a current state
(the open state or the closed state) based on a position of the switch member 361.
In this manner, according to the present modified example, user operability and
usability can be improved.
[0157]
25 Note that, although the acoustic tube 350 is configured by the tubular part
354 and the packing 352 as one end of the cylindrical packing 352 is fitted to the
tubular part 354 that is formed by projection of a part of the partition wall of the rear
housing 330 as described above in the example shown in FIGS. 11A to 14, the
present modified example is not limited thereto. As the acoustic tube 350, another
30 configuration, for example, the acoustic tube 150 shown in FIG. 1 or the acoustic
tube 250 shown in FIG. 6 may be applied.
59
[0158]
The acoustic tube 350 may be configured by the tubular part 354 such that,
for example, the length of the tubular part 354 is formed to be longer. In other
words, the packing 352 may not be provided. In this case, the acoustic tube 350 is
formed to be integrated with the rear housing 330, like the acoustic 5 tube 150 shown
in FIG. 1. Here, in order to plug the opening 356 of the acoustic tube 350 more
reliably and thus set the state in which ventilation does not occur, it is desirable to
form either of the acoustic tube 350 and a member used to plug the opening 356 of
the acoustic tube 350 (the boss 363 in the above example) using an elastic body and
10 to press-fit one into the other. Thus, it is preferable that, when the acoustic tube 350
has the same configuration as the acoustic tube 150 shown in FIG. 1, for example, the
boss 363 of the switch member 361 be formed of an elastic body and the boss 363
formed of the elastic body be press-fitted into the acoustic tube 350. Alternatively,
the opening 356 of the acoustic tube 350 may be plugged such that the switch
15 member 361 has a cylindrical member formed of an elastic body whose one end is
sealed and the other end is opened, and a tip of the acoustic tube 350 may be pressfitted
into the opened end of the cylindrical member.
[0159]
In addition, the acoustic tube 350 may be configured by inserting a tubular
20 member into an opening that does not have a projecting part formed on a partition
wall of the rear housing 330, like the acoustic tube 250 shown in FIG. 6. In this way,
another configuration can also be applied to the acoustic tube 350, like, for example,
the acoustic tube 150 shown in FIG. 1, or the acoustic tube 250 shown in FIG. 6.
[0160]
25 In addition, in the present modified example, a configuration of the acoustic
characteristic adjustment mechanism 360 is not limited to the example described
above. The acoustic characteristic adjustment mechanism 360 can have any of
various types of configurations. Another configuration example of the acoustic
characteristic adjustment mechanism 360 will be described in detail in (5-3. Another
30 configuration example of the acoustic characteristic adjustment mechanism) below.
[0161]
60
(5-2. Acoustic characteristic of a headphone according to the present modified
example)
An acoustic characteristic of the headphone 30 according to the present
modified example will be described with reference to FIG. 16. FIG. 16 is a graph
diagram showing sound pressure level characteristics of the headphone 5 30 according
to the present modified example. In FIG. 16, the horizontal axis represents
frequency, the vertical axis represents sound pressure level, and the sound pressure
level characteristics of the headphone 30 that are obtained from the analysis result of
the acoustic equivalent circuit that corresponds to the headphone 30, which is the
10 same as the acoustic equivalent circuit 40 shown in FIG. 2, are plotted.
[0162]
Referring to FIG. 16, two curves indicating sound pressure level
characteristics are illustrated. The curve J indicated by a solid line in the drawing
indicates the sound pressure level characteristic of the headphone 30 according to the
15 present modified example in the open state, i.e., the state in which ventilation in the
acoustic tube 350 is ensured. The curve K indicated by a dotted line in the drawing
indicates the sound pressure level characteristic of the headphone 30 according to the
present modified example in the closed state, i.e., the state in which ventilation is not
performed in the acoustic tube 350.
20 [0163]
As indicated by the curve J, the headphone 30 in the open state obtains the
stair-like sound pressure level characteristic (in other words, the sound pressure level
characteristic in which a sound pressure level is relatively high in the lower register,
the sound pressure level decreases relatively steeply from the lower register to the
25 middle register, and the sound pressure level shows a relatively little change in the
middle register), like the curve D shown in FIG. 9. On the other hand, referring to
the curve K indicating the sound pressure level characteristic of the headphone 30 in
the closed state, it can be seen that the sound pressure level in the lower register
decreases more drastically than the curve J. The reason for this is considered to be,
30 since ventilation is substantially not performed in the acoustic tube 350 in the closed
state, the amount of air in the rear air chamber 332 is limited, and operations of the
61
vibration plate 312 of the driver unit 310 are suppressed.
[0164]
The acoustic characteristic of the headphone 30 according to the present
modified example has been described above with reference to FIG. 16. It is
possible to appropriately switch a plurality of different acoustic 5 characteristics in the
headphone 30 according to the present modified example according to preference of
a user or peripheral circumstances by providing the acoustic characteristic
adjustment mechanism 360 as described above. Specifically, the sound pressure
level characteristic of the lower register can be adjusted with the acoustic
10 characteristic adjustment mechanism 360.
[0165]
Thus, in a situation in which noise is loud and low-pitched sounds are
hardly heard, for example, on a train, if the headphone 30 is set to the open state, the
sound pressure level in the lower register can be further improved and low-pitched
15 sounds can be more emphasized. Conversely, if the headphone 30 is set to the
closed state in a place in which ambient noise is not very loud, it is possible to cause
the sound pressure level in the lower register to decrease and low-pitched sounds not
to be emphasized more than necessary.
[0166]
20 In addition, it is possible in the headphone 30 to switch the open state and
the closed state with a relatively simple operation, e.g., sliding the switch member
361, as described above. Thus, a user can adjust the acoustic characteristics as
described above more freely and more quickly according to a change in a peripheral
situation.
25 [0167]
Here, comparing the curve K and the curve J, it can be seen that, in the
middle register and the upper register, in particular, in the frequency band in which
the frequency is 1 (kHz) or higher, both curves show substantially the same sound
pressure level characteristic. In the headphone 30 according to the present modified
30 example as described above, even if acoustic characteristics are switched using the
acoustic characteristic adjustment mechanism 360, the sound pressure level
62
characteristic in the middle register and the upper register that are registers relating to
human voices (for example, vocal ranges, or the like) rarely changes. If the sound
pressure level characteristic of the middle register and the upper register remarkably
changes, a user feels a significant change of sound quality, and thus there is a
possibility of the user feeling discomfort. In the present 5 modified example,
however, since only the sound pressure level characteristic of the lower register is
mainly adjusted using the acoustic characteristic adjustment mechanism 360 as
described above, a change of an acoustic characteristic that could give a feeling of
discomfort to a user does not occur.
10 [0168]
Here, the headphone 30 according to the present modified example can, of
course, benefit by having the acoustic tube 350 in the open state, as described in (3.
Acoustic characteristics of the headphone according to the present embodiment)
above. The benefit gained by having the acoustic tube 350 refers to the fact that, in
15 an air-tightened headphone, for example, a difference in sound pressure levels of the
lower register and the middle register and a frequency band that causes the difference
in sound pressure levels can be adjusted, thus an adjustable range of an acoustic
characteristic is widened, and thus fluctuating quality of sound particularly having a
significant difference in sound pressure levels of the lower register and the middle
20 register can be realized. The headphone 30 according to the present modified
example is set to have an acoustic characteristic that can be changed more easily as
necessary while maintaining the advantage gained by having the acoustic tube 350.
[0169]
(5-3. Another configuration example of the acoustic characteristic adjustment
25 mechanism)
The acoustic characteristic adjustment mechanism 360 according to the
present modified example can have any of various configurations in addition to the
configuration described in (5-1. Configuration of the headphone according to the
present modified example) above. Here, another configuration example of the
30 acoustic characteristic adjustment mechanism will be described.
[0170]
63
Although the acoustic characteristic adjustment mechanism 360 is, for
example, constituted by the switch member 361 and has the function of adjusting the
acoustic characteristic of the headphone 30 in two stages by switching the two states
that are the open state or the closed state, the present modified example is not limited
thereto. The acoustic characteristic adjustment mechanism 5 360 may have a
function of adjusting the acoustic characteristic of the headphone 30 in multiple
stages or consecutively. Thus, the acoustic characteristic adjustment mechanism
360, for example, has a function of changing the characteristic of the acoustic tube
350 in multiple stages or consecutively.
10 [0171]
The acoustic characteristic adjustment mechanism 360, for example, may
change an amount of ventilation in the acoustic tube 350 in multiple stages or
consecutively to adjust an acoustic characteristic of the headphone 30 in multiple
stages or consecutively.
15 [0172]
For example, a plurality of notches with different lengths in the longitudinal
direction may be formed in the outer circumferential part of the boss 363.
Accordingly, according to a length of the boss 363 to be inserted into the opening
356 of the packing 352, the number of notches that contribute to ventilation in the
20 acoustic tube 350 changes, in other words, an amount of the ventilation in the
acoustic tube 350 changes, and thus the ventilation in the acoustic tube 350 can be
adjusted by stages.
[0173]
Furthermore, in that configuration, either of the projecting part 364 of the
25 boss 363 and the projecting part 355 of the packing 352 may be provided in a
plurality having a predetermined interval in the longitudinal direction according to a
length of the notches. Accordingly, while the boss 363 is once inserted into the
opening 356 of the packing 352 or the boss 363 is once removed from the opening
356 of the packing 352, contact of the projecting part 364 of the boss 363 and the
30 projecting part 355 of the packing 352 occurs a plurality of times. Thus, the
position of the switch member 361 in the movement direction changes by stages.
64
At this time, the change in the position of the switch member 361 in the movement
direction by stages is linked to a change of an amount of ventilation by stages caused
by differences in the lengths of the notches (for example, ventilation is performed
with one notch in a state in which the switch member 361 moves by one stage,
ventilation is performed with two notches in a state in which the 5 switch member 361
moves by two stages, and the like), and thus a user can know a change of an amount
of ventilation in the acoustic tube 350 by stages based on a position of the switch
member 361 in the movement direction.
[0174]
10 In addition, for example, the notches of the boss 363 may be formed in a
tapered shape (in other words, may be formed such that the amount of notches
gradually changes in the longitudinal direction). Accordingly, it is possible to
consecutively adjust the amount of ventilation in the acoustic tube 350 according to
an amount of the boss 363 to be inserted into the opening 356 of the packing 352.
15 [0175]
In addition, for example, a screw thread may be cut into the outer
circumferential part of the boss 363 and on the inner wall of the opening 356 of the
packing 352 and the boss 363 may be inserted into and removed from the opening
356 while being screwed with the opening 356 of the packing 352. In this case, the
20 acoustic characteristic adjustment mechanism 360 is not a member having a
mechanism that slides in one direction like the switch member 361, but can be
configured with a member having a mechanism that rotates the boss 363 in the
longitudinal direction as an axis of rotation direction. Since insertion and removal
of the boss 363 into and from the opening 356 of the packing 352 are performed
25 using a screw, it is possible to consecutively change an amount of the boss 363 to be
inserted into the opening 356 of the packing 352 at a fixed ratio. By using not only
the screw mechanism but also, for example, the configuration in which the notches of
the boss 363 are formed in the tapered shape as described above, it is possible to
consecutively change an amount of ventilation in the acoustic tube 350.
30 [0176]
Here, the acoustic characteristic adjustment mechanism 360 may change the
65
characteristic of the acoustic tube 350 by changing an element other than the amount
of ventilation in the acoustic tube 350. The acoustic tube 350 functions as the
inductance Mb in the acoustic equivalent circuit as described above. In addition, a
value of the inductance Mb depends on a length and an inner cross-sectional area
(i.e., inner diameter) of the acoustic tube 350. Thus, the acoustic 5 characteristic
adjustment mechanism 360 may have a mechanism that changes the length and the
inner diameter of the acoustic tube 350 to change the length and the inner diameter
and change the inductance Mb of the acoustic tube 350, and thereby adjust the
acoustic characteristic of the headphone 30.
10 [0177]
A configuration example of the acoustic characteristic adjustment
mechanism 360 having the mechanism that changes the length and the inner diameter
of the acoustic tube 350 will be described with reference to FIG. 17. FIG. 17 is an
illustrative diagram for describing the acoustic characteristic adjustment mechanism
15 360 having the mechanism that changes the length and the inner diameter of the
acoustic tube 350.
[0178]
Referring to FIG. 17, an acoustic tube 450 of the present configuration
example is configured such that a second tube 452 is inserted into a first tube 451.
20 Although the illustration of other constituent members is omitted, the acoustic tube
450 spatially connects the rear air chamber 332 of a headphone and the outside
through a tube, and has the same function as the acoustic tubes 150, 250, and 350
shown in FIGS. 1, 6, and 12A to 14.
[0179]
25 The first tube 451 can be provided projecting toward the outside from a
partial region of the partition wall of the housing forming the rear air chamber of the
headphone. The second tube 452 is formed such that the outer diameter thereof is a
little smaller than the inner diameter of the first tube 451, and is configured to be
movable in an insertion direction in a state in which it is inserted into the first tube
30 451.
[0180]
66
When the second tube 452 is inserted into the first tube 451 to a deeper
position (when the second tube 452 is moved in the lower direction of the drawing),
it can be said that the length of the acoustic tube 450 becomes shorter and the inner
diameter thereof becomes smaller. Conversely, when the second tube 452 is moved
to be pulled out from the first tube 451 (when the second tube 5 452 is moved in the
upper direction of the drawing), it can be said that the length of the acoustic tube 450
becomes longer and the inner diameter thereof becomes greater.
[0181]
By moving the second tube 452 in the insertion direction in the present
10 configuration example as described above, the length and the inner diameter of the
acoustic tube 450 can be changed, and an acoustic characteristic of the headphone in
which the acoustic tube 450 is provided can be adjusted. In the present
configuration example, it can be said that an acoustic characteristic adjustment
mechanism is provided to be integrated with the acoustic tube 450.
15 [0182]
Note that, in the configuration example shown in FIG. 17, the acoustic tube
450 may be configured such that the second tube 452 is externally fitted to the first
tube 451. In this case, the second tube 452 can be formed to have an inner diameter
that is slightly greater than the outer diameter of the first tube 451, and in a state in
20 which the first tube 451 is inserted into the second tube 452, the second tube 452 at
the outside can be movable in the insertion direction. By also setting the second
tube 452 to move in the insertion direction in this configuration like the acoustic tube
450 shown in FIG. 17, the length and the inner diameter of the acoustic tube 450 can
be changed.
25 [0183]
Other configuration examples of the acoustic characteristic adjustment
mechanism 360 have been described above. The above-described configuration
examples are, however, mere exemplification of several configurations that the
acoustic characteristic adjustment mechanism 360 can take, and a configuration of
30 the acoustic characteristic adjustment mechanism 360 is not limited to the abovedescribed
configuration examples. The acoustic characteristic adjustment
67
mechanism 360 may have any specific configuration that can change the
characteristic of the acoustic tube 350.
[0184]
(6. Supplement)
It should be understood by those skilled in the art that various 5 modifications,
combinations, sub-combinations and alterations may occur depending on design
requirements and other factors insofar as they are within the scope of the appended
claims or the equivalents thereof.
[0185]
10 In addition, the effects described in the present specification are merely
illustrative and demonstrative, and not limitative. In other words, the technology
according to the present disclosure can exhibit other effects that are evident to those
skilled in the art along with or instead of the effects based on the present
specification.
15 [0186]
Although, for example, the case in which the headphone according to the
present embodiment is a canal earphone has been described above, the present
technology is not limited thereto. The headphone according to the present
embodiment may be a headphone in another form. For example, the headphone
20 according to the present embodiment may be a so-called overhead headphone that
has an air-tightened front air chamber. Here, such overhead headphones are
headphones in which one pair of housings that house a driver unit provided with an
acoustic tube according to the present embodiment are included and the one pair of
housings are linked to each other by a supporting member that curves in an arch
25 shape, and thus the headphones are worn on the head of a user using the supporting
member so that openings provided in the housings through which sounds are output
to the outside face the ears of the user. It is assumed that, when the headphone
according to the present embodiment is an overhead headphone, the sizes of the
housings and the driver unit increase more than when it is a canal earphone. In that
30 case, by appropriately changing values of the elements of the acoustic equivalent
circuit according to a change in the characteristics of the housings and the driver unit,
68
a shape of the acoustic tube can be designed using the same method as that described
above, and the acoustic characteristic can be improved.
[0187]
In addition, although a member that can serve as a resistive component such
as a ventilation resistor is not provided in the acoustic tube according 5 to the present
embodiment in above description, the present technology is not limited thereto.
The acoustic tube according to the present embodiment may be provided with a
ventilation resistor that acts as a resistive component to a flow of air inside the tube.
By providing a ventilation resistor in the acoustic tube, a resistive component can be
10 further imparted to the acoustic equivalent circuit shown in FIG. 2, and acoustic
characteristics of the headphone may be changed. In the present embodiment, by
providing the ventilation resistor in the acoustic tube and appropriately setting a
material and a shape of the ventilation resistor, the acoustic characteristic of the
headphone may be further adjusted.
15 [0188]
Furthermore, other constituent members may be appropriately included in
the housing of the headphone according to the present embodiment according to
application of the headphone, for example, in addition to the configuration shown in
FIG. 6 and FIGS 12A to 13B. Although the case in which the headphone has only
20 one driver unit has been described above, for example, the present embodiment is not
limited thereto. The headphone according to the present embodiment may be, for
example, a so-called multi-way headphone in which a plurality of driver units are
mounted in a housing. Even if there is a change in constituent members included in
the housing in the present embodiment, by appropriately changing elements of the
25 acoustic equivalent circuit or values thereof according to the change, a shape of the
acoustic tube can be designed using the same method as that described above.
[0189]
Additionally, the present technology may also be configured as below.
(1)
30 A headphone including:
a driver unit including a vibration plate;
69
a housing configured to house the driver unit, to form an air-tightened front
air chamber of which a part except for an opening for sound output is spatially
blocked from the outside on a front side on which the vibration plate of the driver
unit is provided, and to form a rear air chamber that has a predetermined capacity on
a rear side that is the opposite side 5 to the front side; and
an acoustic tube provided in a partial region of a partition wall of the
housing that constitutes the rear air chamber and configured to spatially connect the
rear air chamber and the outside of the housing through a tube.
(2)
10 The headphone according to (1), wherein, in an acoustic equivalent circuit
of the headphone, a parallel resonance circuit that causes anti-resonance in a
predetermined resonance frequency is formed at least with an acoustic capacity that
corresponds to a capacity component of the rear air chamber and an acoustic
inductance that corresponds to an inductance component of the acoustic tube.
15 (3)
The headphone according to (2), wherein the acoustic capacity further
includes a capacity component of a driver unit rear air chamber that is formed
between a frame and the vibration plate of the driver unit.
(4)
20 The headphone according to (2) or (3), wherein the resonance frequency is
decided at least based on a value of the acoustic inductance and a value of the
acoustic capacity.
(5)
The headphone according to any one of (1) to (4),
25 wherein a vent hole that spatially connects a driver unit rear air chamber that
is formed between a frame of the driver unit and the vibration plate and the rear air
chamber is provided in the frame,
wherein the vent hole is provided with a ventilation resistor that serves as
resistance in the acoustic equivalent circuit of the headphone, and
30 wherein a sound pressure level of the headphone in a predetermined
frequency band is decided based at least on a value of an acoustic resistance that
70
corresponds to a resistive component of the ventilation resistor in the acoustic
equivalent circuit.
(6)
The headphone according to (5), wherein the sound pressure level of the
headphone in the predetermined frequency band is decided based 5 at least on a value
of an acoustic capacity that corresponds at least to a capacity component of the rear
air chamber, a value of acoustic tube inductance that corresponds to an inductance
component of the acoustic tube in the acoustic equivalent circuit, and a value of the
acoustic resistance.
10 (7)
The headphone according to any one of (1) to (6), wherein the rear air
chamber is spatially blocked from the outside except for ventilation in the acoustic
tube.
(8)
15 The headphone according to (4),
wherein the value of the acoustic inductance is decided according to a
length and an inner cross-sectional area of the acoustic tube, and
wherein the length and the inner cross-sectional area of the acoustic tube are
set such that the resonance frequency has a value from 350 (Hz) to 650 (Hz).
20 (9)
The headphone according to (8), wherein, in the acoustic tube, a ratio of the
length to the inner cross-sectional area is 13 (1/mm) to 45 (1/mm).
(10)
The headphone according to any one of (1) to (9), wherein the housing and
25 the acoustic tube are formed to be integrated.
(11)
The headphone according to any one of (1) to (9),
wherein an opening that spatially connects the rear air chamber and the
outside of the housing is provided in a partial region of a partition wall constituting
30 the rear air chamber of the housing, and
wherein the acoustic tube is configured such that a tubular member is
71
connected to the opening.
(12)
The headphone according to any one of (1) to (11), wherein the driver unit
is a dynamic driver unit.
5 (13)
The headphone according to any one of (1) to (12),
wherein a sound guiding tube that is a tubular portion projecting toward the
outside is formed in one portion of a region constituting the front air chamber of the
housing,
10 wherein the opening for sound output is provided at a tip of the sound
guiding tube, and
wherein the headphone is a canal earphone of which the tip of the sound
guiding tube is inserted into an external auditory canal of a user.
(14)
15 The headphone according to any one of (1) to (12), including:
one pair of housings that house the driver unit,
wherein the one pair of housings are linked to each other by a supporting
member that curves in an arch shape, and
wherein the headphone is an overhead headphone worn on the head of a
20 user using the supporting member so that the opening for sound output of the
housing faces an ear of a user.
(15)
The headphone according to any one of (1) to (14), further including:
an acoustic characteristic adjustment mechanism configured to adjust an
25 acoustic characteristic of the headphone by changing a characteristic of the acoustic
tube.
(16)
The headphone according to (15), wherein the acoustic characteristic
adjustment mechanism adjusts the acoustic characteristic of the headphone by
30 changing ventilation in the acoustic tube.
(17)
72
The headphone according to (16),
wherein the acoustic characteristic adjustment mechanism is constituted by
a switch member that has a boss to be inserted into and removed from the acoustic
tube, and
wherein the boss is inserted into and removed from 5 the acoustic tube
through a parallel movement of the switch member, and ventilation in the acoustic
tube is adjusted.
(18)
The headphone according to (17),
10 wherein at least a partial region of the acoustic tube is formed of an elastic
body, and
wherein the boss is press-fitted to the region of the acoustic tube that is
formed of the elastic body and thereby ventilation in the acoustic tube is obstructed.
(19)
15 The headphone according to (17) or (18),
wherein a first projecting part that projects in a radial direction is formed in
a partial region of the boss in a longitudinal direction,
wherein a second projecting part that projects in the radial direction is
formed in a partial region on an inner wall of the acoustic tube in the longitudinal
20 direction, and
wherein, when the boss is inserted into and removed from the acoustic tube,
the first projecting part and the second projecting part are engaged with and rub
against each other.
(20)
25 An acoustic characteristic adjustment method including:
housing a driver unit that includes a vibration plate in a housing, forming an
air-tightened front air chamber of which a part except for an opening for sound
output is spatially blocked from the outside between the housing and a front side on
which the vibration plate of the driver unit is provided, and forming a rear air
30 chamber that has a predetermined capacity on a rear side that is the opposite side to
the front side; and
73
providing an acoustic tube provided in a partial region of a partition wall of
the housing that constitutes the rear air chamber and configured to spatially connect
the rear air chamber and the outside of the housing through a tube.
Reference 5 Signs List
[0190]
10, 20, 30 headphone
40 acoustic equivalent circuit
110, 210, 310 driver unit
10 116, 216, 316 vent hole
117, 217, 317 ventilation resistor
118, 218, 318 driver unit rear air chamber
120, 220, 320 front housing
125, 225, 325 front air chamber
15 130, 230, 330 rear housing
132, 232, 332 rear air chamber
140, 240, 340 housing
150, 250, 350 acoustic tube
360 acoustic characteristic adjustment mechanism
20
74
CLAIMS
Claim 1
A headphone comprising:
a driver unit including a vibration plate;
a housing configured to house the driver unit, to form an 5 air-tightened front
air chamber of which a part except for an opening for sound output is spatially
blocked from the outside on a front side on which the vibration plate of the driver
unit is provided, and to form a rear air chamber that has a predetermined capacity on
a rear side that is the opposite side to the front side; and
10 an acoustic tube provided in a partial region of a partition wall of the
housing that constitutes the rear air chamber and configured to spatially connect the
rear air chamber and the outside of the housing through a tube.
Claim 2
15 The headphone according to claim 1, wherein, in an acoustic equivalent
circuit of the headphone, a parallel resonance circuit that causes anti-resonance in a
predetermined resonance frequency is formed at least with an acoustic capacity that
corresponds to a capacity component of the rear air chamber and an acoustic
inductance that corresponds to an inductance component of the acoustic tube.
20
Claim 3
The headphone according to claim 2, wherein the acoustic capacity further
includes a capacity component of a driver unit rear air chamber that is formed
between a frame and the vibration plate of the driver unit.
25
Claim 4
The headphone according to claim 2, wherein the resonance frequency is
decided at least based on a value of the acoustic inductance and a value of the
acoustic capacity.
30
Claim 5
75
The headphone according to claim 1,
wherein a vent hole that spatially connects a driver unit rear air chamber that
is formed between a frame of the driver unit and the vibration plate and the rear air
chamber is provided in the frame,
wherein the vent hole is provided with a ventilation resistor 5 that serves as
resistance in the acoustic equivalent circuit of the headphone, and
wherein a sound pressure level of the headphone in a predetermined
frequency band is decided based at least on a value of an acoustic resistance that
corresponds to a resistive component of the ventilation resistor in the acoustic
10 equivalent circuit.
Claim 6
The headphone according to claim 5, wherein the sound pressure level of
the headphone in the predetermined frequency band is decided based at least on a
15 value of an acoustic capacity that corresponds at least to a capacity component of the
rear air chamber, a value of acoustic tube inductance that corresponds to an
inductance component of the acoustic tube in the acoustic equivalent circuit, and a
value of the acoustic resistance.
20 Claim 7
The headphone according to claim 1, wherein the rear air chamber is
spatially blocked from the outside except for ventilation in the acoustic tube.
Claim 8
25 The headphone according to claim 4,
wherein the value of the acoustic inductance is decided according to a
length and an inner cross-sectional area of the acoustic tube, and
wherein the length and the inner cross-sectional area of the acoustic tube are
set such that the resonance frequency has a value from 350 (Hz) to 650 (Hz).
30
Claim 9
76
The headphone according to claim 8, wherein, in the acoustic tube, a ratio of
the length to the inner cross-sectional area is 13 (1/mm) to 45 (1/mm).
Claim 10
The headphone according to claim 1, wherein the housing 5 and the acoustic
tube are formed to be integrated.
Claim 11
The headphone according to claim 1,
10 wherein an opening that spatially connects the rear air chamber and the
outside of the housing is provided in a partial region of a partition wall constituting
the rear air chamber of the housing, and
wherein the acoustic tube is configured such that a tubular member is
connected to the opening.
15
Claim 12
The headphone according to claim 1, wherein the driver unit is a dynamic
driver unit.
20 Claim 13
The headphone according to claim 1,
wherein a sound guiding tube that is a tubular portion projecting toward the
outside is formed in one portion of a region constituting the front air chamber of the
housing,
25 wherein the opening for sound output is provided at a tip of the sound
guiding tube, and
wherein the headphone is a canal earphone of which the tip of the sound
guiding tube is inserted into an external auditory canal of a user.
30 Claim 14
The headphone according to claim 1, comprising:
77
one pair of housings that house the driver unit,
wherein the one pair of housings are linked to each other by a supporting
member that curves in an arch shape, and
wherein the headphone is an overhead headphone worn on the head of a
user using the supporting member so that the opening for 5 sound output of the
housing faces an ear of a user.
Claim 15
The headphone according to claim 1, further comprising:
10 an acoustic characteristic adjustment mechanism configured to adjust an
acoustic characteristic of the headphone by changing a characteristic of the acoustic
tube.
Claim 16
15 The headphone according to claim 15, wherein the acoustic characteristic
adjustment mechanism adjusts the acoustic characteristic of the headphone by
changing ventilation in the acoustic tube.
Claim 17
20 The headphone according to claim 16,
wherein the acoustic characteristic adjustment mechanism is constituted by
a switch member that has a boss to be inserted into and removed from the acoustic
tube, and
wherein the boss is inserted into and removed from the acoustic tube
25 through a parallel movement of the switch member, and ventilation in the acoustic
tube is adjusted.
Claim 18
The headphone according to claim 17,
30 wherein at least a partial region of the acoustic tube is formed of an elastic
body, and
78
wherein the boss is press-fitted to the region of the acoustic tube that is
formed of the elastic body and thereby ventilation in the acoustic tube is obstructed.
Claim 19
The headphone 5 according to claim 17,
wherein a first projecting part that projects in a radial direction is formed in
a partial region of the boss in a longitudinal direction,
wherein a second projecting part that projects in the radial direction is
formed in a partial region on an inner wall of the acoustic tube in the longitudinal
10 direction, and
wherein, when the boss is inserted into and removed from the acoustic tube,
the first projecting part and the second projecting part are engaged with and rub
against each other.
15 Claim 20
An acoustic characteristic adjustment method comprising:
housing a driver unit that includes a vibration plate in a housing, forming an
air-tightened front air chamber of which a part except for an opening for sound
output is spatially blocked from the outside between the housing and a front side on
20 which the vibration plate of the driver unit is provided, and forming a rear air
chamber that has a predetermined capacity on a rear side that is the opposite side to
the front side; and
providing an acoustic tube provided in a partial region of a partition wall of
the housing that constitutes the rear air chamber and configured to spatially connect
25 the rear air chamber and the outside of the housing through a tube.