DESCRIPTION
SPEAKER APPARATUS AND AUDIO OUTPUT METHOD
TECHNICAL FIELD
The present invention relates to a speaker
apparatus and an audio output method, and is preferable
for application in obtaining an audio image with a sense
of spread by exciting a pipe wall of a cylindrical member
with a sound wave from a sounding body that is driven on
10 the basis of an audio signal and radiating the sound wave
outward from the entire outer surface of the cylindrical
member.
BACKGROUND ART
15 Conventionally, there has been proposed a speaker
system that reproduces sound by adding vibration to an
acoustic diaphragm by a magnetostrictive actuator (refer
to Patent Document 1, for example).
In a speaker system 1 , as shown in Fig. 1, a
20 cylindrical acoustic diaphragm 10 formed of an aciylic
resin or the like is vertically supported on a discoid
base housing 20, and four magnetostrictive actuators 30
are arranged at equiangular intervals in the base housing
20.
25 In the speaker system 1, a drive rod 35 for each
magnetostrictive actuator 30 abuts on a lower end surface
12 of the acoustic diaphragm 10 to drive the
magnetostrictive actuator 30 by an audio signal, so that
the magnetostrictive actuator 30 adds vibration to the
30 lower end surface 12 of the acoustic diaphragm 10 in a
direction perpendicular to the lower end surface 12 of
1
the acoustic diaphragm 10.
The lower end surface 12 of the acoustic diaphragm
10 is excited by a longitudinal wave, which mixes with a
transverse wave to be a mixed wave by the propagation of
5 a vibration elastic wave in a planar direction (a
direction parallel to the surface) of the acoustic
diaphragm 10, whereby a sound wave is radiated in the
planar direction of the acoustic diaphragm 10 to form a
uniform audio image across the entire height direction of
10 the acoustic diaphragm 10.
Although omitted in this speaker system 1, it is
also described in Patent Document a. that a regular
speaker unit is installed in a central opening part of
the base housing 20.
15 In this case, the acoustic diaphragm 10 functions
as a tweeter in charge of an upper range of an audible
frequency range, and the regular speaker unit functions
as a woofer in charge of a lower range of the audible
frequency range.
20 On the other hand, there has been proposed
acoustic device including an active diaphragm provided in
a spherical resonator and a passive diaphragm provided in
a position facing the active diaphragm of the resonator
(refer to Patent Document 2, for example).
25
CITATION LIST
PATENT DOCUMENTS
Patent Document 1: Japanese Patent Application Laid-Open
No. 2007-228557
30 Patent Document 2: Japanese Patent Application Laid-Open
No. 01-253396
2
SUMMARY OF THE INVENTION
Now, the speaker system 1 described in Patent
Document 1 has had a problem of insufficient output of
5 sound in a low pitch range due to a structure that the
regular speaker unit alone is in charge of the lower
range.
The speaker system 1 has also had problems that,
since the upper part of the acoustic diaphragm 10 is open,
10 a filter is required for eliminating resonance of a high
degree, and dust enters the speaker system.
In consideration of the above respects, the present
invention proposes a speaker apparatus and an audio
output method, the speaker apparatus having a simple
15 structure, excellent designability and satisfactory
acoustic characteristics and capable of further enhancing
the low pitch range without increasing the size.
In order to solve such problems, the present
invention is provided with: a cylindrical member open on
20 one end side and the other end side; a sounding body that
is coaxial with the cylindrical member, arranged at the
one end side of the cylindrical member, and driven on the
basis of an audio signal; and a diaphragm that is coaxial
with the cylindrical member, installed at the other end
25 side of the cylindrical member, and vibrates in response
to a sound wave that passes through the cylindrical
member. While the cylindrical member functions as a.
resonance tube by being excited to vibration with the
sound wave that is radiated from the sounding body and
30 passes through the cylindrical member, the diaphragm
functions as a passive radiator by vibrating in response
3
to the sound wave passing through the cylindrical member.
While the cylindrical member functions as the
resonance tube by being excited to vibration with the
sound wave passing through the cylindrical member, the
5 diaphragm functions as the passive radiator in response
to the sound wave passing through the cylindrical member.
Therefore, the output of sound in the lower range can be
further enhanced than heretofore performed with excellent
designability without making a significant change in the
10 appearance of the cylindrical member or increasing the
size thereof.
In the present invention, the sound wave radiated
from the sounding body on the basis of the audio signal
passes through the cylindrical member, the sounding body
15 being coaxial with the cylindrical member opened on the
one end side and the other end side and being arranged at
the one end side of the cylindrical member. Also, in the
present invention, the diaphragm that is coaxial with the
cylindrical member and installed at the other end side of
20 the cylindrical member functions as the passive radiator
by vibrating in response to the sound wave that is
radiated from the sounding body and passes through the
cylindrical member.
While the cylindrical member functions as the
25 resonance tube by being excited to vibration with the
sound wave passing through the cylindrical member, the
diaphragm functions as the passive radiator in response
to the sound wave passing through the cylindrical member.
Therefore, the output of sound in the lower range can be
30 further enhanced than heretofore performed with excellent
designability without making a significant change in the
4
appearance of the cylindrical member or increasing the
size thereof.
According to the present invention, the cylindrical
member functions as the resonance tube by being excited
5 to vibration with the sound wave passing through the
cylindrical member, and the diaphragm functions as the
passive radiator in response to the sound wave passing
through the cylindrical member, thereby allowing the
output of sound in the lower range to be further enhanced
10 than heretofore without making a significant change in
the appearance of the cylindrical member or increasing
the size thereof. In this manner, the speaker apparatus
and the audio output method can be realized, the speaker
apparatus having the simple structure, the excellent
15 designability and the satisfactory acoustic
characteristics and capable of further enhancing the low
pitch, range without increasing the size.
BRIEF DESCRIPTION OF DRAWINGS
20 Fig. 1 is a schematic perspective view illusarating
a. construction of a conventional speaker system.
Fig. 2 is a schematic perspective view illustration
an overall construction of a speaker apparatus,
Fig. 3 is a schematic longitudinal section
25 illustrating a cross-sectional construction of the
speaker apparatus.
. 4 is a set of schematic top views illustrating
a construction of a top surface of the speaker apparatus.
Fig. 5 is a schematic bottom view illustrating a.
30 construction of a bottom surface of the speaker apparatus.
Fig. 6 is a schematic view used to describe a
5
correlation coefficient.
Fig. 7 is a schematic view illustrating a
correlation coefficient when there are two actuators.
Fig. 8 is a set of schematic views illustrating a
change in an audio image according to a correlation
coefficient between two audio signals, where r12 = 1 in
Fig. 8 (A), r12 = 0 in Fig. 8 (B), and r12 = -1 in Fig. 8
(C).
Fig. 9 is a schematic view illustrating correlation
10 coefficients when there are four actuators.
Fig. 10 (A) is a schematic view illustrating one
example of an audio image state when viewed from above,
and Fig. (B) is a schematic view illustrating one example
of the audio image state when viewed obliquely from a
15 side.
Fig. 11 is a schematic view illustrating one
example of a drive method when performing monaural
reproduction.
Fig. 12 is a schematic view illustrating one
20 example of a drive method when performing stereo
reproduction.
Fig. 13 is a schematic view illustrating one
example of a drive method when performing surround
reproduction.
25 Fig. 14 is a schematic view illustrating an audio
image state when the surround reproduction is performed.
Fig. 15 is a schematic view provided to describe a
state of sound wave radiation.
Fig. 16 (A) is a schematic view illustrating
30 characteristics without a passive radiator, and Fig. 16
(B) is a schematic view illustrating the characteristics
6
with a passive radiator. These are schematic views.
Fig. 17 is a schematic cross-sectional view
illustrating an edge-cum-diaphragm irradiated with light
that propagates through a pipe.
Fig. 18 is a schematic view illustrating an. overall
construction of a speaker apparatus according to another
embodiment.
Fig. 19 is a schematic view illustrating a crosssectional
construction of the speaker apparatus according
10 to the other embodiment.
Fig. 20 is a schematic view provided to describe a
state of sound wave radiation according to the other
embodiment.
Fig. 21 is a schematic view illustrating a pipe
15 construction according to the other embodiment.
Fig. 22 is a schematic view illustrating a
construction of an edge-cum-diaphragm according to the
other embodiment.
Fig. 23 is a schematic view illustrating a
20 construction of the edge-cum-diaphragm according to the
other embodiment.
MODE FOR CARRYING OUT THE INVENTION
Modes for carrying out the invention will be
25 described below in the following order.
1. Embodiment
2. Another Embodiment
<1. Embodiment>
[1-1. Structure of a speaker apparatus]
30 As shown in Figs. 2 to 5, a speaker apparatus 100
includes a base housing 101, a pipe 102, a piezoelectric
7
actuator 103, and a speaker unit 104 using an electric
actuator (not shown) as a sounding body.
The base housing 101 is formed of a synthetic resin,
for example, and is formed into a disk shape, a center
5 part of which is provided with an opening 105 penetrating
through the base housing in a cylindrical shape. The
base housing 101 is also provided with three legs 106
planted at equal intervals along an outer circumference
side of a bottom surface of the base housing, for example.
10 The base housing 101 can achieve stable
installation by including three legs 1.06 as compared to
four legs, for example, since these three legs 106 would
be surely brought into contact with an installation
surface.
15 Furthermore, the bottom surface of the base housing
101 can be separated from the installation surface by the
legs 106 provided on the bottom surface of the base
housing 101, thereby allowing a sound wave from the
speaker unit 104 installed on the bottom surface side of
20 the base housing 101 to be radiated outside.
The pipe 102 includes a cylindrical acoustic
diaphragm and is formed of a transparent acrylic resin
with a translucent property or a light-guiding property,
for example. The pipe 102 is fixed to the base housing
25 2.01.
That is, the lower end of the pipe 102 is fixed to
a top surface of the base housing 101 at a plurality of
positions, four positions in the present embodiment, by
using a metal L-shaped angle 107. The size of the pipe
30 102 here is 1000 mm in length, 120 mm in diameter, and 3
mm in thickness, for example.
8
Moreover, an outer frame 102.A on the upper end
surface of the pipe 102 (Fig. 3) is integrally adhered to
a transparent edge-cum--diaphragm 102B of a predetermined
thickness (approximately 0.3 mm) made of a urethane
material by, for example, a transparent adhesive. The
edge-cum-diaphragm 102B and the speaker unit 104 of the
base housing 101 are disposed at positions to face each
other.
As a result, the edge-cum-diaphragm 102B of the
10 pipe 102 is adapted to function as a passive radiator for
the speaker unit 104 of the base housing 101.
This transparent edge-cum-diaphragm 102B is
attached to the transparent pipe 102 via the outer frame
102A on the upper end surface of the pipe 102 by the
15 transparent adhesive, thereby maintaining transparency
from the pipe 102 to the edge-cum-diaphragm 102B,
constructing the appearance that can hardly be considered
as a speaker, and allowing the designability to be
improved as an interior accessory.
20 Incidentally, the outer frame 102A of the speaker
apparatus 100 is also formed of a transparent acrylic
resin so that a completely transparent state can be
formed from the pipe 102 to the edge-cum-diaphragm 102B.
Here, the edge-cum-diaphragm 102B functioning as
25 the passive radiator is constructed such that an edge
part EG and a diaphragm part BC are formed integrally.
Therefore, there is no need to individually tune the edge
part and the diaphragm part after sticking them together,
as conventionally performed. Simply, the edge-cum-
30 diaphragm 102B as a whole needs tuning.
In this case, although not shown, a round hole for
9
screwing is formed at one end and the other end of the Lshaped
angle 107. One end of this L-shaped angle 107 is
screwed to the top surface of the base housing 101 via a
screw 7.09.
5 A screw groove (not shown) for being screwed
together with a screwing part of the screw 109 is formed
on the base housing 101. In this case, a damping
material 108 formed of a ring-shaped rubber material or
the like is interposed between the one end of the L-
10 shaped angle 107 and the top surface of the base housing
101.
Furthermore, the other end of the L-shaped angle
107 is screwed to the lower end of the pipe 102 through a
screw 110 and a nut 111. A round hole (not shown) for
2.5 passing a screwing part of the screw 110 is formed at the
lower end of the pipe 102.
Damping materials 112 and 113 formed of a ringshaped
rubber material or the like are interposed between
the other end of the L-shaped angle 107 and the outer
20 surface of the pipe 102, and between the nut 111 and the
inner surface of the pipe 102, respectively.
In the speaker apparatus 100, the damping materials
1087 112, and 113 interposed in this manner would inhibit
vibration (an elastic wave) by the piezoelectric actuator
25 103 from being propagated into the base housing 101
through the pipe 102 and the L-shaped angle 107, thereby
preventing the audio image from being localized to the
side of the base housing 101.
In this speaker apparatus 100, moreover, four
30 piezoelectric actuators 103 are fixed to the base housing
101 and disposed at equal intervals along the circular
10
end surface at the lower end side of the pipe 102. The
piezoelectric actuator 103 is driven by voltage, and a
drive rod 103A thereof includes a transmission part for
transmitting a displacement output.
In this case, a storage hole 114 for storing the
piezoelectric actuator 103 is formed in the base housing
101, and the piezoelectric actuator 103 is fixed to the
base housing 101 by being stored in this storage hole 114,
Four piezoelectric actuators 103 are used in the
10 present embodiment. However, a current-driven
magnetostrictive actuator or an electrodynamic actuator
may also be used, for example.
The speaker apparatus 100 in this case uses the
voltage-driven piezoelectric actuators 103 and thus
15 consumes less electric current than the current-driven
actuator, which would result in advantages of less amount
of heat generated and a longer service life of a battery.
Here, a damping material 115 formed of a. rubber
material or the like is interposed between the base of
20 the storage hole 114 and the piezoelectric actuator 103,
thereby inhibiting the vibration by the piezoelectric
actuator 103 from being propagated into the base housing
101-and preventing the audio image from being localized
to the side of the base housing 101.
25 The drive rod 103A of the piezoelectric actuator
103 would be in a state abutting on the end surface of
the pipe 102 on the lower end sidethereof when the
piezoelectric actuator 103 is stored and fixed to the
storage hole 114 of the base housing 101.
30 In this case, a displacement direction of the drive
rod 103A is also a planar direction (a direction parallel
11
to the surface) of the pipe 102. In the speaker
apparatus 100, the pipe 102 can be vibrated from the end
surface on the lower end side thereof with the vibration
component directed orthogonal to the end surface, by
means of the piezoelectric actuators 103 arranged in the
above manner.
At this time, the end surface on the lower end side
of the pipe 102 is excited by a longitudinal wave, which
mixes with a transverse wave to be a mixed wave by the
10 propagation of a vibration elastic wave in the planar
direction (the direction parallel to the surface) of the
pipe 102, whereby the mixed wave is radiated in the
planar direction of the pipe 102 to form a uniform audio
image across the entire height direction of the pipe 102.
15 In this manner, the pipe 102 includes a speaker in
charge of an upper range side of an audible frequency
range to function as a tweeter, the speaker unit 104
includes a speaker in charge of a lower range side of the
audible frequency range to function as a woofer, and the
20 edge-cum-diaphragm 102B functions as the passive radiator
that enhances a low-pitched sound from the speaker unit
104.
The speaker unit 104 is installed by using a screw
(not shown), for example, in a position corresponding to
25 the opening 105 on the bottom surface side of the base
housing 101 while facing downward. In this case, a
central axis of the speaker unit 104 is directed in the
same way as an axis of the pipe 102.
The sound wave of a positive phase output from the
30 front of this speaker unit is radiated outside from the
bottom surface side of the base housing 101. When the
12
sound wave of a negative phase output from the rear
surface of the speaker unit 104 reaches the edge-cumdiaphragm
102B through the opening 105 and the pipe 102,
the pipe 102 functions as a resonance tube to output
heavy lower range sound and, at the same time, the edgecum-
diaphragm 102B functions as the passive radiator.
In this case, the speaker apparatus 100 can further
enhance the lower range sound by including both the
function as the resonance tube by means of the pipe 102
10 and the function as the passive radiator by means of the
edge-cum-diaphragm 102B.
Also, a damping material 116 formed of a rubber
material or the like is arranged between the end surface
on the lower end side of the pipe 102 and the base
15 housing 101. As shown in Fig. 4(B), the damping material
116 is formed in a ring shape as a whole and provided
with a through-hole 116A for passing therethrough the
drive rod 103A of the piezoelectric. actuator 103.
Therefore, in the speaker apparatus 100,the damping
20 material 116 would prevent the vibration by the
piezoelectric actuator 103 from being propagated into the
base housing 101 through the pipe 102. At the same time,
the`pipe 102 can satisfactorily function as the resonance
tube with the increased airtightness provided by the
25 damping material 116.
In addition to such construction, the speaker
apparatus 100 (Figs. 3 and 4) includes a total of six LED
(Light Emitting Diode) light bulbs 132 installed at 60-
degree intervals on stays 131 arranged to cover the rear
30 surface side of the speaker unit 104, on the rear surface
side of the speaker unit 104 installed to the opening 105
13
of the base housing 101. Note that the LED light bulb
132 may simply be an LED,
In addition, the speaker apparatus 100 is provided
with a substantially discoid diffuser panel 133 installed
5 on a driver part 104D of the speaker unit 104 so as to
cover the LED light bulb 132.
Consequently, the speaker apparatus 100 is adapted
to irradiate the edge-cum-diaphragm 102B from inside
after diffusing irradiation light from the LED light bulb
10 132 with a diffuser panel 133 and making the irradiation
light pass through the pipe 102 as diffused light.
The edge-cum-diaphragm 102B is also a diaphragm
with a light-diffusing property, that is, a lightdiffuser
panel. The diffused light having passed through
15 the pipe 102 is further diffused by the edge-cumdiaphragm
102B and then radiated outside.
Functioning as the passive radiator, the edge-cumdiaphragm
102B vibrates in synchronization with the lowpitched
sound output from the speaker unit 104. As a
20 result, the speaker apparatus 100 forms a light emission
state in which the sound from the speaker unit 104 and
from the vibration of the edge-cum-diaphragm 102B is
synchronized with the light radiated in conjunction with
the vibration of the edge-cum-diaphragm 1028.
25 Here, the pipe 102 is formed of an acrylic resin
with a translucent property or a light-guiding property
but may also contain a fluorescent paint.
For example, a fluorescent paint for plastics named
Lumogen F (registered trademark) Dyes by BASF Corporation
30 may be used as the fluorescent paint.
In effect, the pipe 102 would concentrate light on
14
the entire surface thereof and emit strong fluorescence
from the edge (the end surface) by containing the
fluorescent paint of approximately 0.02% of the mass of
the acrylic resin forming the pipe 102.
The Lumogen F (registered trademark) Dyes include
Orange240 (trade name), Yellow083 (trade name), Red305
(trade name) and the like.
When Orange240 (trade name) is used, for example,
the entire pipe 102 would appear transparent orange, and
10 the upper end surface thereof (shielded by the outer
frame 102A in this case) would intensely glow orange.
Moreover, when a letter is scratched and traced on
the outer side surface of the pipe 102, the letter
portion would glow intensely. This letter portion would
15 glow by an external fluorescence light, the sunlight or
the like without turning on the LED light bulb 132.
Therefore, the speaker apparatus 100 is adapted
such that a user can easily visually recognize the letter
portion traced on the pipe 102 under the operating
20 environment in which the external light is provided to
the pipe 102 even when the LED light bulb 132 is turned
off.
The Lumogen F (registered trademark) Dyes are also
superior in light resistance (a residual ratio of
25 fluorescence). The pipe 102 containing Orange240 (trade
name) with fluorescence intensity of 100 before exposure
would have the fluorescence intensity of 85 after being
exposed for 2000 hours under a certain condition.
[1-2. A method for driving a speaker]
30 Next, a drive system of the speaker apparatus 100
will be described. In this speaker apparatus 100, the
15
four piezoelectric actuators 103 are independently
provided with drive signals that have no mutual
correlation in order to expand the audio image outside
the pipe 102. A principle of this will be described with
5 a case where two actuators are used.
Now, there is an index called a correlation
coefficient r for indicating a degree of similarity
between two audio signals, for example. As shown in Fig.
6, the correlation coefficient r takes a value from +1 to
10 -1.
Specifically, the correlation coefficient r would
be 1 (4-1) when the two audio signals are completely
identical, would be 0 when the two audio signals are
independent or unrelated, and would be -1 when the two
15 audio signals are in mutually opposite phases.
In effect, as shown in Fig. 7, an audio signal for
driving the piezoelectric actuator 103 on the left side
is let to be Al, an audio signal for driving the
piezoelectric actuator 103 on the right side is let to be
20 A2, and the correlation coefficient between the audio
signals Al and A2 is let to be r12, when vibration is to
be added to the lower end surface of the cylindrical pipe
102-by the piezoelectric actuator 103 in a planar
direction perpendicular to the lower end surface of the
25 pipe.
Considering the relationship between the
correlation coefficient r12 and the audio image, as shown
in Fig. H (A), an audio image Ai would be formed in the
central part inside the pipe 102 within a surface
30 orthogonal to the central axis of the pipe 102 when the
correlation coefficient is r12 = 1. There would be no
16
sense of spread in the audio image.
Specifically, the audio signals Al and A2 would
each be a synthesized signal obtained by the sum of a
left audio signal and a right audio signal of a stereo
5 audio signal when the correlation coefficient is rl2 = 1,
for example.
When the correlation coefficient is r12 = 0, the
audio image Ai would include, within the surface
orthogonal. to the central axis of the pipe 102, circular
10 audio image portions AilO and Ai20 inside the
piezoelectric actuators 103 on the left side and the
right side, respectively, and an audio image portion Ai30
between the circular audio image portions AilO and Ai20,
as shown in Fig. 8 (S).
15 Specifically, the audio signal Al would be the left
audio signal of the stereo audio signal, and the audio
signal A2 would be the right audio signal of the stereo
audio signal when the correlation coefficient is r12 = 0,
for example.
20 When the correlation coefficient is r12 = -1, the
audio image Ai would include, within the surface
orthogonal to the central axis of the pipe 102, semicircular
audio image portions Ail and Ail outside the
piezoelectric actuators 103 on the left side and the
25 right side, respectively, as shown in Fig. 8 (C). There
would be a sense of spread in the audio image Ai.
Specifically, the audio signal Al would be the
synthesized signal obtained by the sum of the left audio
signal and the right audio signal of the stereo audio
30 signal, and the audio signal A2 would be a signal in a
phase opposite from that of the audio signal Al when the
17
correlation coefficient is r12 = -1, for example.
Accordingly, in the speaker apparatus 100, the two
piezoelectric actuators 103 are independently driven by
the two audio signals Al and A2 made non-correlated so
that the correlation coefficient r12 of the audio signals
would be less than 1. The non-correlation is achieved by
performing phase shift, delay or arithmetic operation
(synthesis) on the audio signals.
[1-3. A drive method and an audio image state]
10 As shown in Fig. 9, the speaker apparatus 100 in
the present embodiment includes a piezoelectric actuator
103 on the upper side and a piezoelectric actuator 103 on
the lower side in addition to the piezoelectric actuators
103 on the left and right sides.
15 In this case, let the audio signal for driving the
piezoelectric actuator 103 on the upper side be Al, the
audio signal for driving the piezoelectric actuator 103
on the right side be A2, the audio signal for driving the
piezoelectric actuator 103 on the lower side be A3, and
20 the audio signal for driving the piezoelectric actuator
103 on the left side be A4.
Then, there would be six correlation coefficients r
including: the correlation coefficient r12 between the
audio signals Al and A2; a correlation coefficient r13
25 between the audio signals Al and A3; a correlation
coefficient r14 between the audio signals Al and A4; a
correlation coefficient r23 between the audio signals A2
and A3; a correlation coefficient r24 between the audio
signals A2 and A4; and a correlation coefficient r34
30 between the audio signals A3 and A4.
The audio signals Al, A2, A3, and A4 are processed
18
to be mutually non-correlated such that these six
correlation coefficients r12, r13, r14, r23, r24, and r34
would all be sufficiently smaller than 1, namely, a value
close to -1 or 0.
As a result, as shown in Figs. 10 (A) and 10 (B),
the audio image Ai by the audio signals Al, A2, A3, and
A4 of the speaker apparatus 100 would be formed into a
ring shape as a whole on the outer side of the pipe 102
within the surface orthogonal to the central axis of the
10 pipe 102, thereby obtaining the sense of spread from the
audio image.
Specific methods of driving a speaker when
performing the monaural reproduction, the stereo
reproduction, and the surround reproduction. will be
15 described below.
[1-4. A drive method when performing the monaural
reproduction]
As a drive method when performing the monaural
reproduction, audio signals are made non-correlated by
20 shifting a phase of an audio signal, as shown in Fig. 11.
Specifically, in this drive method, an original
monaural audio signal Me is supplied to the piezoelectric
actuator 103 on the upper side as is, and the phase of
the monaural audio signal Mo is delayed (or advanced) 90°
25 by a 90° phase-shift circuit 51 to be supplied to the
piezoelectric actuator 103 on the right side as a
monaural audio signal Mi.
Then, in this drive method, the phase of the
monaural audio signal M1 is delayed (or advanced) 90° by
30 a. 90° phase-shift circuit 52 to be supplied to the
piezoelectric actuator 103 on the lower side as a
19
monaural audio signal M2, the phase of which is then
delayed (or advanced) 90° by a 90° phase-shift circuit 53
to be supplied to the piezoelectric actuator 103 on the
left side as a monaural audio signal M3.
5 in this drive method, as shown in Fig. 9, the six
correlation coefficients r12, r13, r14, r23, r24, and r34
are all made non-correlated and, as shown in Fig. 10, the
audio image Ai with a sense of spread is formed on the
outer side of the pipe 102.
10 [1-5. A drive method when performing the stereo
reproduction]
As a drive method when performing the stereo
reproduction, audio signals are made non-correlated by
inverting a phase of an audio signal as shown in Fig. 12,
15 for example.
Specifically, in this drive method, an original
left audio signal Lo is directly supplied to the
piezoelectric actuator 103 on the upper side as one left
audio signal La, and the phase of the left audio signal
20 Lo is inverted by a phase inversion circuit 61 to obtain
another left audio signal Lb, the phase of which is
inverted from that of the one left audio signal La. The
left audio signal Lb is then supplied to the
piezoelectric actuator 103 on the lower side.
25 Likewise, in this drive method, an original right
audio signal Ro is directly supplied to the piezoelectric
actuator 103 on the right side as one right audio signal
Ra, and the phase of the right audio signal Ro is
inverted by a phase inversion circuit 62 to obtain
30 another right audio signal Rb, the pha.se of which is
inverted from that of the one right audio signal Ra. The
20
right audio signal Rb is then supplied to the
piezoelectric actuator 103 on the left side.
Thus, in this drive method, the correlation
coefficient r13 (Fig. 9) between the left audio signals
5 La and Lb would be -1, and the correlation coefficient
r24 between the right audio signals Ra and Rb would also
be -1, thereby forming the audio image Ai with the sense
of spread on the outer side of the pipe 102.
In this drive method, a listener can listen to
10 music such that the left audio signal is positioned on
the left side seen from the listener and the right audio
signal is positioned on the right side seen from the
listener, even when the listener listens to the music
from a direction shown by an arrow 9A or an arrow 9B.
15 When the listener listens from a fixed direction,
however, the left audio signals La and Lb may be supplied
to the mutually adjacent piezoelectric actuators 103 on
the upper and right sides, and the right audio signals Ra
and Rb may be supplied to the mutually adjacent
20 piezoelectric actuators 103 on the lower and left sides.
Incidentally, other drive methods when performing
the stereo reproduction include: an example of shifting
the-phase of the audio signal by 90° to achieve the noncorrelation;
an example of delaying (or advancing) the
25 phase of the audio signal by 90° to achieve the noncorrelation;
an example of delaying the audio signal by a
predetermined amount of time to achieve the noncorrelation;
an example of achieving the non-correlation
by two comb filters having mutually complementary
30 frequency characteristics; and an example of achieving
the non-correlation by a Schroeder circuit.
21
[1-6. A drive method when performing the surround
reproduction]
In a drive method when. performing the surround
reproduction, an original left audio signal Lo is
5 directly supplied to the piezoelectric actuator 103 on
the lower left side as a left audio signal L, and an
original right audio signal Ro is directly supplied to
the piezoelectric actuator 103 on the lower right side as
a right audio signal R, as an example shown in Fig. 13.
10 At the same time, a signal (Lo-Ro) non-correlated
to each of the left audio signal L (Lo) and the right
audio signal R (Ro) is obtained by subtracting the right
audio signal Ro from the left audio signal Lo by an
arithmetic circuit 77. This signal (Lo-Ro) is then
15 supplied to the piezoelectric actuator 103 on the upper
left side as a surround left audio signal SL.
Likewise, a signal (Ro-Lo) non-correlated to each
of the left audio signal L (Lo) and the right audio
signal R (Ro) is obtained by subtracting the left audio
20 signal Lo from the right audio signal Ro by an arithmetic
circuit 78. This signal (Ro-Lo) is then supplied to the
piezoelectric actuator 103 on the upper right side as a
surround right audio signal SR.
The surround right audio signal SR would also be
25 non-correlated to the surround left audio signal SL, that
is, the surround left audio signal SL and the surround
right audio signal SR would be mutually non-correlated.
In effect, a front audio image Af is formed inside
the pipe 102 between the piezoelectric actuators 103 on
30 the lower left side and the lower right side when the
listener listens to acoustic sound being reproduced from
22
a direction shown by an arrow 9c, as shown in Fig. 14.
On the other hand, a rear audio image Ar is formed
outside the pipe 102 from the vicinity of the
piezoelectric actuator 103 on the upper left side to the
vicinity of the piezoelectric actuator 103 on the upper
right side. The front audio image Af and the rear audio
image Ar together would make it multidirectional as a
whole.
Note that the drive method when performing the
10 surround reproduction is not limited to the
aforementioned method but can also be used by means of
various other methods.
[1-7. Operation of a speaker apparatus]
Now, operation of the speaker apparatus 1.00 (Figs.
15 2 to 5) will be described.
In the speaker apparatus 100, the four
piezoelectric actuators 103 stored and fixed to the base
housing 101 are driven by the four kinds of audio signals
that are mutually non-correlated, the individual drive
20 rods 103A are displaced in response to the respective
audio signals, and the pipe 102 is vibrated by the
vibration component from the end surface on the lower end
side of the pipe 102 in a direction orthogonal to the end
surface (a planar direction).
25 At-this time, the end surface on the lower end side
of the pipe 102 is excited to vibration by the
longitudinal wave, and the elastic wave (vibration) is
propagated into the pipe 102 in the planar direction.
This elastic wave repeats a mode conversion of the
30 longitudinal wave, the transverse wave, the longitudinal
wave. ...... to be the mixed wave of the longitudinal wave
23
and the transverse wave when being propagated into the
pipe 102. The vibration in an in-plane direction of the
pipe 102 (a direction perpendicular to the surface) is
excited by the transverse wave and, as a result, the
speaker apparatus 100 radiates the sound wave from the
pipe 102.
That is, the speaker apparatus 100 can obtain sound
in a high pitch range output from the outer surface of
the pipe 102.
10 In this speaker apparatus 100, the four
piezoelectric actuators 103 arranged at equal intervals
along the circular end surface on the lower end side of
the pipe 102 are driven by the four audio signals that
are mutually non-correlated, thereby forming the ring-
15 shaped audio image on the outer side of the pipe 102. As
a result, a user can obtain the sense of wide spread from
the audio image.
Also in the speaker apparatus l00, as shown in Fig.
15, a sound wave SWF of a positive phase can be obtained
20 by a lower range component of the audio signal from the
front surface of the speaker unit 104 installed on the
bottom surface side of the base housing 101, and a sound
wave SWB of a negative phase can be obtained by the lower
range component of the audio signal from the back surface
25 of the speaker unit.
The sound wave SWF obtained from the front surface
of the speaker unit 104 is radiated outward from the
bottom surface side of the base housing 101. In addition,
the sound wave SWB obtained from the back surface of the
30 speaker unit 104 passes through the opening 105 and the
pipe 102 to approach the edge-cum-diaphragm 102E
24
installed on the upper end surface.
This pipe 102 is formed light and thin to the
extent the pipe can be excited to vibration by the sound
wave SWB. As a result, the pipe wall of the pipe 102 is
5 excited to vibration by the sound wave of the negative
phase (air density) SWB passing through the pipe 102.
The pipe wall of the pipe 102 is excited to
vibration in response to the sound wave SWB of the
negative phase to function as the resonance tube, whereby
10 a sound wave SWS of the positive phase is radiated
outward from the entire outer surface of the pipe 102,
the sound wave SWS corresponding to the audio signal
associated with driving the speaker unit 104.
Consequently, a user can feel uniform sound pressure at
15 each position in a longitudinal direction of the pipe 102
and obtain the audio image that is spread throughout the
pipe 102.
In this speaker apparatus 100,. the upper part of
the pipe 102 is closed by the edge-cum-diaphragm 102B.
20 Therefore, a sound wave of the negative phase (not shown),
which is generated inside the pipe 102 when the pipe
vibrates in response to the sound wave SWB of the
negative phase, would be confined inside the pipe 102 and
not be radiated outside.
25 Asia result, the speaker apparatus 100 can
eliminate in advance an adverse influence of the sound
wave of the negative phase with respect to the sound wave
SWS of the positive phase that is radiated outside from
the entire outer surface of the pipe 102, thereby
30 allowing satisfactory acoustic characteristics to be
obtained as compared to the case where the edge-cum-
25
diaphragm 102B is not installed.
In the speaker apparatus 100, moreover, the edgecum-
diaphragm 102B as the passive radiator vibrates in
response to the sound wave SWB heading outside from the
5 rear surface of the speaker unit 104 through the opening
105 and the pipe 102. In consequence, the sound wave SWB
with the further enhanced low pitch range would be
radiated outside through the edge-cum-diaphragm 1028.
Accordingly, the speaker apparatus 100 can output
10 low-pitched sound that is further enhanced compared to
conventional devices by means of the sound wave SWS
radiated outside from the entire outer surface of the
pipe 102 and the sound wave SWB radiated outside through
the edge-cum-diaphragm 102B as the passive radiator,
15 That is to say, the speaker apparatus 100 can
obtain: sound in a high pitch range output from the outer
surface of the pipe 102 by the vibration added from the
four piezoelectric actuators 103; sound in the low pitch
range output from the entire outer surface of the pipe
20 102 by the pipe wall thereof being vibrated by the sound
wave SWB of the negative phase from the speaker unit 104
and functioning as the resonance tube; and sound in the
further enhanced low pitch range output by the edge-cumdiaphragm
102B functioning as the passive radiator by the
25 sound wave SWB of the negative phase from the speaker
unit 104.
[1-8. Characteristics caused by the passive radiator]
In the speaker apparatus 100 (Figs. 2 and 3), the
edge-cum-diaphragm 102B is installed as the passive
30 radiator on the upper end surface of the pipe 102. Here,
the difference in frequency characteristics between the
26
cases where the passive radiator is and is not actually
installed will be examined.
As shown in Fig. 16 (A.), a sound pressure
characteristic SL and an impedance characteristic IL will
5 have patterns shown in a graph when the passive radiator
(the edge-cum-diaphragm 102B) is not installed to the
pipe 102 of the speaker apparatus 100.
As for the impedance characteristic IL, in this
case, a frequency fl (approximately 80 Hz) at a trough
10 portion called a dip would be the resonance point for the
entire pipe 102.
At this time, with regards to the sound pressure
characteristic SL, a first resonance occurs at the
resonance point, and high-order resonances including a
15 third, a fifth and a seventh resonance occur at a
frequency P1 around about 240 Hz, a frequency P2 around
about 400 Hz, and a frequency P3 of about 560 Hz,
respectively.
On the other hand, as shown in Fig. 16 (B), the
20 sound pressure characteristic SL and the impedance
characteristic IL will have patterns shown in a graph
when the passive radiator (the edge-cum-diaphragm 102B)
is installed to the pipe 102 of the speaker apparatus 100.
In this case, as for the impedance characteristic
25 IL, a frequency f1' (approximately 65 Hz) at a dip would
be the resonance point for the entire pipe 102 and the
edge-cum-diaphragm 1028. As for the sound pressure
characteristic SL, the first resonance occurs in an area
AR that includes a frequency band of the resonance point.
30 That is, as for the sound pressure characteristic
SL, the frequency band of the resonance point lowered
27
from the frequency fl (approximately 80 Hz) to the
frequency fl' (approximately 65 Hz) has allowed for the
sound in the still lower pitch range to be reproduced,
indicating that its sound pressure level has also been
5 increased,
With respect to the sound pressure characteristic
SL, moreover, the high-order resonances including the
third, fifth and seventh resonances occur at a frequency
Pl' around about 205 Hz, a frequency P2' around about 340
10 Hz, and a frequency 23' of about 500 Hz, respectively.
Nonetheless, the frequency bands are lowered on the whole,
and peak levels are greatly decreased as compared to the
case where the passive radiator is not installed (Fig. 16
(A)) .
15 In this manner, by installing the passive radiator
(the edge-cum-diaphragm 102B) to the pipe 102, the
speaker apparatus 100 is adapted to suppress the highorder
resonance of an odd-numbered order that is not
pleasant for a human ear and enhance the output of sound
20 in the further lower pitch range as compared to the case
where the passive radiator is not installed.
In effect, the speaker apparatus 100 can enhance
the output in the low pitch range without making a user
perceive a particularly major change in appearance, by
25 means of-a simple structure in. which the edge-cumdiaphragm
102B as transparent as the pipe 102 is
installed without varying the length and the diameter
(volume) of the pipe 102.
Particularly in the speaker apparatus 100, a lower
30 range reproduction frequency is determined according to
the length of the pipe 102 that functions as the
28
resonance tube. When the resonance tube and the passive
radiator are used, the lower range reproduction frequency
is determined according to the length of the resonance
tube, stiffness (mobility of the diaphragm) of the
5 passive radiator, and the weight of the passive radiator
itself (the edge-cum-diaphragm 102B weighs 4.2 [g] in
this case).
That is to say, the speaker apparatus 100 is
adapted to be capable of controlling the lower range
10 reproduction frequency by optimizing the stiffness and
the mass of the passive radiator (the edge-cum-diaphragm
102B) with respect to the pipe 102 (weighing 1232 [g] in
this case), even when the length of the pipe 102 as the
resonance tube is not sufficient.
15 Conversely, the speaker apparatus 100 can have the
shorter pipe 102 than heretofore set to achieve further
downsizing, since the reproduction of sound in the yet
lower pitch range can be realized even when the length of
the pipe 102 as the resonance tube is not sufficient.
20 [1-9. Illumination effect through the passive radiator]
In this speaker apparatus 100 (Fig. 3), the
irradiation light from the total of six LED light bulbs
132-disposed at 60-degree intervals on the stays 131
disposed to cover the rear surface side of the speaker
25 unit 104-is diffused by the diffuser panel 133 and passes
through the pipe 102 as the diffused light.
At this time, in the speaker., apparatus 100, the
diffused light diffused by the diffuser panel 133 is
reflected off the inner surface of the pipe 102, reaches
30 the edge-cum-diaphragm 102B thereafter, and irradiates
the edge-cum-diaphragm 1028, as shown in Fig. 17,
29
The pipe 102 here is formed of the acrylic resin
having the translucent property or the light-guiding
property as mentioned above, thereby reflecting the
diffused light diffused by the diffuser panel 133 off the
5 inner surface of the pipe 102 and efficiently bringing
the light to reach the edge-cum-diaphragm 1023.
The edge-cum-diaphragm 102B is also a light
diffuser panel with the light-diffusing property and thus
further diffuses the diffused light having passed through
10 the pipe 102 to radiate it to the outside.
Here, the edge-cum-diaphragm 102B functions as the
passive radiator and vibrates in synchronization with the
low-pitched sound output from the speaker unit 104. As a
result, the speaker apparatus 100 can form the light
15 emission state in which the sound from the speaker unit
104 and from the vibration of the edge-cum-diaphragm 1023
is in synchronization with the light radiated through the
edge-cum-diaphragm 1023.
[1-10. Operation and effect]
20 With the construction above, the edge-cum-diaphragm
1023, which is provided on the other end side of the pipe
102 to face the speaker unit 104 on the one end side of
the-pipe 102, functions as the passive radiator for
enhancing the low pitch range in the speaker apparatus
25 100.
In the speaker apparatus 100, the speaker unit 104
requires an electrical connection to supply the audio
signal.. On the other hand, the electrical connection is
not required for the edge-cum-diaphragm 102B that
30 vibrates in response to the sound wave of the negative
phase radiated from the rear surface of the speaker unit
30
104, thereby allowing the structure to be simplified.
The speaker apparatus 100 can obtain the effect of
efficiently enhanced low-pitched sound by the combination
of the pipe 102 and the edge-cum-diaphragm 102B, since
5 the edge-cum-diaphragm 102B functions as the passive
radiator, and the pipe wall of the pipe 102 is excited to
vibration by the sound wave SEB of the negative phase
from the rear surface of the speaker unit 104 and
functions as the resonance tube.
10 Moreover, the speaker apparatus 100 appears no
different from the conventional structure in which no
passive radiator is provided because both of the pipe 102
and the edge-cum-diaphragm 102B are transparent and
invisible to a user's eye. Therefore, the speaker
15 apparatus would neither have to give the user any special
sense of discomfort nor lose the original designability.
Furthermore, the inner space of the pipe 102 of the
speaker apparatus 100 is sealed from above by the edgecum-
diaphragm 102B provided at the upper end of the pipe
20 102. As a result, the speaker apparatus would be able to
prevent dust from entering the pipe in advance and avoid
an adverse influence on sound resulting from the motions
of the piezoelectric actuator 103 and the drive rod 103A
being obstructed by the dust.
25 Moreover, the edge-cum-diaphragm 102E of the
speaker apparatus 100 is constructed such that the edge
part EG and the diaphragm part BC are formed integrally.
Therefore, there is no need to individually tune the edge
part and the diaphragm part after sticking them together,
30 as heretofore performed. Simply, the edge-cum-diaphragm
102B as a whole needs tuning, which can resolve the
31
complication at the time of manufacturing.
According to the above construction, the speaker
apparatus 100 can enhance the low pitch range without
complicating the construction thereof nor increasing the
5 size of the pipe 102 by making the edge-cum-diaphragm
102B function as the passive radiator for enhancing the
low pitch range, the edge-cum-diaphragm 102B being
provided at the other end side of the pipe 102 in a
manner facing the speaker unit 104 provided at the one
10 end side of the pipe 102.
<2. Another embodiment>
Described in the aforementioned embodiment is the
case where sound is output from the entire outer surface
of the pipe 102 by vibrating the pipe 102 with the
15 vibration component directed orthogonal to the end
surface on the lower end side of the pipe 102 from the
end surface through the drive rod 103A of the
piezoelectric actuator 103. However, the present
invention may also be adapted to excite and vibrate the
20 pipe wall of the pipe 102 by means of the sound wave of
the negative phase radiated from the rear surface side of
the speaker unit 104 alone without using the
piezoelectric actuator 103.
Specifically, as shown in Figs. 18 to 20 in which
25 parts corresponding to those in Fig. 2 are assigned the
same reference signs as Fig. 2, a speaker apparatus 200
includes a base housing 101, a pipe 222, and a speaker
unit 104 using an electrodynamic actuator, and does not
include the piezoelectric actuator 103 that directly
30 vibrates the pipe 102 as is the case for the speaker
apparatus 100.
32
The pipe 222 is formed light and thin to the extent
that the pipe 222 can vibrate in response to a sound wave
from the speaker unit 104. For example, this pipe 222 is
formed of a polycarbonate or an acrylic resin with a.
5 thickness of 0.5 mm.
The pipe 222 is opened on one end side and the
other end side, where the lower end on the one end side
is fixed to a top surface of the base housing 101 by
using an adhesive, for example, and an edge-cum-diaphragm
10 102E as described above is installed on the other end
side through an outer frame 102A.
The pipe 222 has a diameter substantially identical
to a diameter of an opening 105 formed in the base
housing 101 in order to function as a resonance tube. At
15 the same time, the pipe 222 is fixed in position with
respect to the opening 105.
The speaker unit 104 is installed by using a screw
(not shown), for example, in a position corresponding to
the opening 105 on the bottom surface side of the base
20 housing 101 while facing downward. The speaker unit 104
is disposed on the same axis as the pipe 222 and driven
on the basis of an audio signal.
A sound wave SWF (Fig. 20) of a positive phase
output from the front surface of the speaker unit 104 is
25 radiated; outside from the bottom surface side of the base
housing 101. A sound wave SWB of a negative phase output
from the rear surface of the speaker unit 104 passes
through the opening 105 and the pipe 222 and is radiated
outside in a state where a low pitch range has been
30 enhanced through the edge-cum-diaphragm 102B provided on
the upper end side of the pipe 222.
33
A pipe wall of the pipe 222 vibrates in response to
the sound wave SWB of the negative phase that passes
through the pipe 222, whereby a sound wave SWS
corresponding to the audio signal associated with driving
the speaker unit 104 is radiated outward from the entire
outer surface of the pipe 222. As a consequence, a user
can feel uniform sound pressure at each position in a
longitudinal direction of the pipe 222 and thus obtain an
audio image that is spread throughout the pipe 222.
10 In addition to the pipe 222 functioning as the
resonance tube, the edge-cum-diaphragm 102B disposed in
the position facing the speaker unit 104 functions as a
passive radiator, thereby further enhancing the low pitch
range.
15 Moreover, in the case described in the
aforementioned embodiment, the edge-cum-diaphragm 102B
formed of a urethane material is installed to the outer
frame 102A on the upper end surface,of the pipe 102.
However, the present invention may also have a
20 construction in which an edge formed of a urethane
material is installed to the outer frame 102A, and a
diaphragm formed of materials such as the acrylic resin,
carbon, paper and various other materials is installed to
the edge.
25 Furthermore, the transparent edge-cum-diaphragm
102B formed of the urethane material is used in the
aforementioned embodiment. However, the present
invention may also use the transparent edge-cum-diaphragm
102B formed of an ester material or of a styrene material
30 if the edge-cum-diaphragm 102B does not need to be
transparent.
34
Furthermore, the cylindrical pipe 102 is used in
the aforementioned embodiment. However, the present
invention may also use a pipe 232 such that the diameter
thereof gradually becomes larger in a traveling direction
the sound wave SWB from the speaker unit 104, as shown
in Fig. 21, for example.
In this case, the pipe 232 can exert the same
effect as when the pipe 102 is used. In addition, having
the gradually larger diameter in the traveling direction
10 of the sound wave SWB from the speaker unit 104, the pipe
232 would have the increased electrical inductance
component and can obtain both flattening of frequency
characteristics and a. damping effect of resonance.
Having a wide outlet from which the sound wave SWB is
15 radiated, the pipe 232 can also obtain the effect in
which the audio image can be spread more widely.
Moreover, in the aforementioned embodiment, the
edge-cum-diaphragm 102E is installed via the outer frame
102A. However, as shown in Fig. 22, the present
20 invention may also have a construction such that an edgecum-
diaphragm 25213 is directly adhered to the upper end
of the pipe 102 without using the outer frame 102A and
that an outer frame 252A is installed so as to cover the
ends of the edge-cum-diaphragm 252B and the pipe 102.
25 In this case, the outer diameter of the pipe 102
corresponds with that of the edge-cum-diaphragm 25213, so
that the edge-cum-diaphragm 252B would be present
throughout the inner diameter of the pipe 102. As a
result, the entire surface of the edge-cum-diaphragm 252B
30 would ideally operate as a passive radiator by the direct
sound wave SWE output from the rear surface of the
35
speaker unit 104.
Furthermore, in this case, the vibration by the
piezoelectric actuator 103 of the pipe 102 would be
propagated from an excitation point to the upper end
5 surface. A reflected wave generated on the upper end
surface would be suppressed by the edge part EG of the
edge-cum-diaphragm 252B, thereby preventing a standing
wave from being generated by the reflected wave.
Furthermore, in the aforementioned embodiment, the
10 edge-cum-diaphragm 102B is installed via the outer frame
102A. However, as shown in Fig. 23, the present
invention may also have a construction such that a cone
paper 220 and a cap 221 as used in a typical speaker unit
are installed in place of the edge-cum-diaphragm 102B via
15 the outer frame 102A.
Furthermore, in the aforementioned embodiment, the
speaker apparatus of the present invention includes the
pipe 102 as the cylindrical member,,the speaker unit 104
as the sounding body, and the edge-cum-diaphragm 102B as
20 the diaphragm. However, the speaker apparatus of the
present invention may also include the cylindrical member,
the sounding body and the diaphragm that are formed by
various other constituents.
25 INDUSTRIAL APPLICABILITY
The speaker apparatus and the audio output method
of the present invention may be applicable to a speaker
apparatus integrated into an audio-visual apparatus such
as a television other than being used by itself as the
30 speaker apparatus, for example.
36
REFERENCE SIGNS LIST
100, 200 Speaker apparatus
101 Base housing
102, 222, 232 Pipe
5 1028, 2328, 252B Edge-cum-diaphragm
103 Piezoelectric actuator
104 Speaker unit
105 Opening
106 Leg
10 107 L-shaped angle
108, 112, 113, 115, 116Damping material
131 Stay
132 LED light bulb
133 Diffuser panel
15 220 Cone paper
221 Cap

CLAIMS
1. A speaker apparatus comprising:
a cylindrical member open on one end side and the
5 other end side;
a sounding body that is coaxial with the
cylindrical member, arranged on the one end side of the
cylindrical member, and driven on the basis of an audio
signal; and
10 a diaphragm that is coaxial with the cylindrical
member, installed on the other end side of the
cylindrical member, and vibrates in response to a sound
wave that passes through the cylindrical member,
wherein the cylindrical member functions as a
15 resonance tube by being excited to vibration with the
sound wave that is radiated from the sounding body and
passes through the cylindrical member, and the diaphragm
functions as a passive radiator by vibrating in response
to the sound wave that passes through the cylindrical
20 member.
2. The speaker apparatus according to claim 1,
comprising an actuator configured to add a vibration
component in a direction orthogonal to an end surface of
25 the cylindrical member.
3. The speaker apparatus according to claim 2,
wherein the cylindrical member outputs sound in a
high pitch range from an outer surface thereof by
30 vibration added by the actuator, and outputs sound in a
low pitch range from the outer surface of the cylindrical
38
member by being excited to vibration with the sound wave
that is radiated from the sounding body and passes
through the cylindrical member.
4. The speaker apparatus according to claim 1 or 3,
wherein the diaphragm is integrally formed with the
cylindrical member on the other end side thereof.
5. The speaker apparatus according to claim 4,
10 wherein the cylindrical member and the diaphragm
are formed of a transparent member.
6. The speaker apparatus according to claim 3,
comprising a light source provided on a rear surface side
15 of the sounding body,
wherein light from the light source is received by
the diaphragm to generate a light emission state
synchronized with vibration of the diaphragm.
20 7. An audio output method comprising:
making a sound wave pass through a cylindrical
member, the sound wave being coaxial with the cylindrical
member opened on one end side and the other end side and
being radiated on the basis of an audio signal from a
25 sounding:bod.y arranged on the one end side of the
cylindrical member; and
vibrating a diaphragm, which is coaxial.. with the
cylindrical member and installed on the other end side of
the cylindrical member, in response to the sound wave
30 that is radiated from the sounding body and passes
through the cylindrical member, thereby allowing the
39
diaphragm to function as a passive radiator.