Title of Invention: HEADPHONE DEVICE
Technical Field
[OOOl]
The present invention relates to a headphone device and
specifically, a headphone device including a speaker array
which has a plurality of speaker units.
Background Art
[0002]
Conventional studies have been carried out related to
sound field reproduction method. Regarding speaker
reproduction, surround reproduction such as 5.1 ch. and 7.1
ch. is generally proposed and is commercialized. An
advantage of this technique is to use speakers called rear
surround sound speakers, as well as front speakers and in
combination they are capable of reproducing rear and
environmental sounds.
[0003]
However, a problem arises during the surround sound
reproduction to find the best ideal sound field point for
listening in a service area of the installation center, of
which is limited. In addition, in surround sound
reproduction, there is a problem that it is difficult to
arrange the speakers in a rear position in an actual home.
[0004]
As a measure to solve the problem concerning the
speaker arrangement, there is a front surround speaker using
a transoral technique. In the front surround speaker,
virtual surround sound can be enjoyed by using only the
front speaker and using a head-related transfer function.
The advantage of the technique is that the speaker can be
easily installed and the system is simple. On the other
hand, there is a problem that individual variations in the
effect may occur because the head-related transfer function
is used. In addition, also in the technique, there is a
problem concerning the listening position that the ideal
position for the reproduction is limited.
[0005]
As a measure to solve the problem concerning the
listening position, there is a sound field reproduction
technique using wave field synthesis (see, NPL 1). This is
such a technique that the sound field inside a closed curved
surface can be completely controlled if a speaker array is
configured, and a sound pressure having the closed curved
surface shape which does not include a sound source and a
particle velocity in the normal direction can be completely
controlled. When using the sound field reproduction
technique which uses wave field synthesis, the sound field
inside the closed curved surface is completely reproduced
and the degree of freedom of the listening position is also
increased.
[0006]
For example, in PTL 1, a three-dimensional sound field
reproduction device is disclosed in which a plurality of
speakers of the speaker array cover the entire head of the
listener and a high level of realism can be reproduced.
However, in the three-dimensional sound field reproduction
device, since the plurality of speakers are used and to
configure the array is needed, there is a problem that the
scale becomes large. In addition, in a case of using the
speaker array, there is a problem in that the frequency band
to be reproduced is limited by the distance between the
speakers due to a problem of spatial aliasing.
[0007]
On the other hand, in the field of headphone
reproduction, there is a virtual surround sound using the
head-related transfer function. When using the virtual
surround, it is possible to ideally enjoy sound field with a
handy headphone device and the problem concerning the
listening position does not occur.
Citation List
Patent Literature
[0008]
PTL 1: Japanese Unexamined Patent Application
Publication No. 2008-118559
Non Patent Literature
[0009]
NPL 1: "Study on Three-Dimensional Virtual Reality
based on Kirchhoff's Integral Equation", Waseda University,
Advance Research Institute for Science and Engineering,
Acoustic Laboratory, Yoshio YAMAZAKI, [online], April, 1997,
(search October 1, 20101, Internet
Summary of Invention
Technical Problem
[OOlO]
However, as described above, in virtual surround sound
using the head-related transfer function in the field of the
headphone reproduction, since the sound pressure in the
vicinity of an entrance of the external auditory meatus is
duplicated as "a point", there is a problem that influence
of the individual auricle cannot be considered and an ideal
effect cannot be obtained depending on an individual. In
addition, generally, since the headphone has a shape
blocking the ear, there is a problem that external sound
cannot be heard even though a feeling of being out of the
head may be obtained with virtual surround sound.
[ 0 0 11 ]
An object of the present invention is to provide a
headphone device in which the influence of individual
differences in virtual sound field reproduction is less
likely to occur and which is capable of listening to the
external sound naturally.
Solution to Problem
[0012]
The concept of the present invention is a headphone
device including:
a speaker array formed of a plurality of speaker units
arranged to surround an auricle,
wherein the speaker array reproduces a sound field
inside a closed curved surface in the vicinity of the
auricle using a wave field synthesis.
[0013]
In the present invention, the speaker array is included.
The speaker array formed of the plurality of speaker units
arranged to surround the auricle. Then, the sound field
inside the closed curved surface in the vicinity of the
auricle is reproduced by the speaker array using the wave
field synthesis. In this case, a sound pressure signal as a
driving signal for causing the sound emitted at each
position of speaker units is supplied to the plurality of
speaker units of the speaker array so as to reproduce the
sound f i e l d i n s i d e t h e closed curved surface i n the v i c i n i t y
of the a u r i c l e .
[ 0 0 14 ]
As described above, i n the present invention, the sound
f i e l d i n s i d e t h e closed curved surface i n the v i c i n i t y of
the a u r i c l e is reproduced by the speaker array using the
wave f i e l d s y n t h e s i s , and since reverberation or a
d i f f r a c t i o n e f f e c t occurs i n the ear of an i n d i v i d u a l , t h e
influence caused by i n d i v i d u a l d i f f e r e n c e s is l e s s l i k e l y t o
occur. In addition, i n the present invention, the speaker
array is formed of the p l u r a l i t y of the speaker u n i t s
arranged t o surround t h e a u r i c l e and is not of a shape t h a t
blocks the ear of the l i s t e n e r , and then the external sound
can be heard n a t u r a l l y .
[0015]
In the present invention, f o r example, the p l u r a l i t y of
speaker u n i t s of the speaker array may be arranged t o be
i n c l i n e d inwardly towards the closed curved surface.
Accordingly, a propagation v e l o c i t y of the p a r t i c l e s i n a l l
up and down, and l e f t and r i g h t d i r e c t i o n s can be reproduced
s a t i s f a c t o r i l y i n s i d e the closed curved surface. For
example, the headphone device may f u r t h e r include a donutshaped
ear pad having an opening portion i n which the
a u r i c l e may be i n s e r t e d , and the p l u r a l i t y of speaker u n i t s
of the speaker array may be arranged along a c i r c u l a r end
portion which is opposite to an abutting side of a listener
of the ear pad.
[0016]
Further, in the present invention, for example, a
distance Ad [m] of the plurality of the speaker units of the
speaker array may satisfy a formula of Ad < c/(2*fmax), when
a reproduction maximum frequency is fmax [Hz] and a sound
velocity is c [m/s]. Accordingly, a frequency band up to
the reproduction maximum frequency fmax [Hz] can be
reproduced.
Advantageous Effects of Invention
[0017]
According to the present invention, the influence of
individual differences in the virtual sound field
reproduction is less likely to occur and the external sound
may be heard naturally. In other words, since the sound
field inside the closed curved surface in the vicinity of
the auricle is reproduced by the speaker array using the
wave field synthesis, and reverberation or a diffraction
effect occurs in the ear of an individual, the influence
caused by individual differences is less likely to occur.
In addition, the speaker array has the plurality of the
speaker units arranged to surround the auricle and is not of
a shape that blocks the ear of the listener, and then the
external sound can be heard naturally.
Brief Description of Drawings
[0018]
[Fig. 11 Fig. 1 is a view illustrating a configuration
example of a headphone device as an embodiment of the
present invention.
[Fig. 21 Fig. 2 is a view illustrating an example of a
closed curved surface in which a sound field is reproduced
by a speaker array included in a headphone body.
[Fig. 31 Fig. 3 is a view for explaining that a
plurality of speaker units of the speaker array included in
the headphone body arranged to be inclined inwardly towards
the closed curved surface in which the sound field is
reproduced.
[Fig. 41 Fig. 4 is a view for explaining that the
plurality of the speaker units of the speaker array are
arranged along a circular end portion of an ear pad which is
opposite to an abutting side of a listener.
[Fig. 51 Fig. 5 is a view for explaining an arrangement
distance of the plurality of the speaker units of the
speaker array included in the headphone body.
[Fig. 61 Fig. 6 is a block diagram illustrating a
configuration example of a circuit which supplies a sound
pressure signal to each speaker unit of the speaker array
included in the headphone body.
Description of Embodiments
[0019]
H e r e i n a f t e r , a mode ( r e f e r r e d t o as "an embodiment"
below) f o r c a r r y i n g o u t the present invention w i l l be
described. I n a d d i t i o n , the description w i l l be made i n the
following order.
1. Embodiment
2. Modification Example
[0020]
<1. Embodiment>
[Configuration Example of Headphone Device]
Figs. l ( a ) t o ( c ) i l l u s t r a t e a configuration example of
a headphone device 100 as the embodiment. Fig. l ( a ) is a
top view, Fig. 1 (b) is a f r o n t view and Fig. 1 ( c ) is a side
view thereof. The headphone device 100 is configured such
t h a t a l e f t - s i d e headphone body 120L and a r i g h t - s i d e
headphone body 120R a r e connected t o f r o n t end portions of
the l e f t and r i g h t of a head band 110, r e s p e c t i v e l y .
[0021]
The l e f t - s i d e headphone body 120L has a speaker array
130. The speaker array 130 is formed of a p l u r a l i t y of
speaker u n i t s 131 which a r e arranged t o surround the a u r i c l e
( l e f t - s i d e ) of a l i s t e n e r . The speaker array 130 included
i n the l e f t - s i d e headphone body 120L reproduces a sound
f i e l d inside a c l o s e d curved surface 140L i n the v i c i n i t y of
the a u r i c l e ( l e f t - s i d e ) i l l u s t r a t e d i n Fig. l ( b ) using a
wave field synthesis. A sound pressure signal as a driving
signal for causing the sound to be emitted at each position
of speaker units 131 is supplied to a plurality of speaker
units 131 of the speaker array 130 included in the left-side
headphone body 120L so that the sound field inside the
closed curved surface 140L can be reproduced.
[0022]
The right-side headphone body 120R also has the speaker
array 130. The speaker array 130 is formed of a plurality
of the speaker units 131 which are arranged to surround the
auricle (right-side) of a listener. The speaker array 130
included in the right-side headphone body 120R reproduces a
sound field inside a closed curved surface 140R in the
vicinity of the auricle (right-side) illustrated in Fig.
l(b) using the wave field synthesis. The sound pressure
signal as the driving signal for causing the sound to be
emitted at each position of speaker units 131 is supplied to
a plurality of speaker units 131 of the speaker array 130
included in the right-side headphone body 120R so that the
sound field inside the closed curved surface 140R can be
reproduced.
[0023]
In addition, with respect to the wave field synthesis,
a detailed description thereof will be omitted, however, for
example, there is a method or the like in which the
Kirchhoff's integral formula is used as indicated in the
"Study on Three-Dimensional Virtual Reality based on
Kirchhoff's Integral Equation", Yoshio YAMAZAKI. In the
method, the sound field inside a closed curved surface S is
reproduced by discretizing the closed curved surface S at N
points and by reproducing a sound pressure P (rj) and a
particle velocity un (rj) at the N points on-the closed
curved surface S. In the embodiment, the sound pressure
signal supplied to each of the speaker units 131 of the
speaker array 130 included in the headphone bodies 120L and
120R is generated, based on the wave field synthesis
described above.
[0024]
Fig. 2(a) illustrates an example of the closed curved
surface 140L in which the sound field is reproduced by the
speaker array 130 included in the left-side headphone body
120L. The closed curved surface 140L is a narrow region
having a diameter of 8 to 10 cm around the external auditory
meatus when viewed from the side head portion of the human
(the listener). Fig. 2(b) illustrates a positional
relationship between the left-side headphone body 120L and
the closed curved surface 140L in a case where the headphone
100 is mounted. In addition, even though detailed
description is omitted, similarly, the closed curved surface
140R in which the sound field is reproduced by the speaker
array 130 included in the right-side headphone body 120R is
a narrow region having a diameter of 8 to 10 cm around the
external auditory meatus.
[0025j
As illustrated in Fig. 3, the plurality of speaker
units 131 of the speaker array 130 included in the headphone
bodies 120L and 120R are arranged to be inclined inwardly
towards the closed curved surfaces 140L and 140R in which
the sound field is reproduced. In other words, a central
axis S of each speaker unit 131 is inclined towards a
central axis Z of the speaker array 130. As described above,
since the plurality of the speaker units 131 of the speaker
array 130 are arranged to be inclined, a propagation
velocity of the particles in all directions of up and down,
and left and right can be reproduced satisfactorily inside
the closed curved surfaces 140L and 140R.
[0026]
In Fig. 1 described above, even though the illustration
is omitted, the headphone bodies 120L and 120R include
donut-shaped ear pads 150 having opening portions in which
the auricle can be inserted, respectively. As illustrated
in Fig. 4, the plurality of the speaker units 131 of the
speaker array 130 described above are arranged along a
circular end portion 150a of the ear pad 150, which is
opposite to an abutting side of the listener.
[0027]
As illustrated in Fig. 5, the plurality of the speaker
units 131 of the speaker array 130 included in the headphone
bodies 120L and 120R are arranged having a distance Ad [m].
The distance Ad [m] satisfies the following formula (I),
when a reproduction maximum frequency is fmax [Hz]. In this
regard, c is a sound velocity (approximately, 340 m/s).
Accordingly, a frequency band up to the reproduction maximum
frequency fmax [Hz] can be reproduced.
Ad
In addition, the above embodiment is illustrated in
such a manner that the plurality of the speaker units 131
are arranged in a circle in the speaker array 130 included
i n the headphone bodies 120L and 120R. However, the
p l u r a l i t y of speaker u n i t s 131 may not be arranged i n a
c i r c l e and it may be arranged i n an e l l i p s e , i n a square or
i n other shapes. In a word, speaker u n i t s may be arrahged
t o surround the a u r i c l e . I n a d d i t i o n , the above embodiment
is i l l u s t r a t e d i n such a manner t h a t the p l u r a l i t y of the
speaker uni-ts 131 a r e arranged i n a single c i r c l e i r i the
speaker a r r a y 130 included i n the headphone bodies 120L and
120R, however, a configuration which is arranged i n double
c i r c l e s or t r i p l e c i r c l e s may be considered.
Reference Signs L i s t
[0036]
100 headphone device
110 head band
120 headphone body
120L l e f t - s i d e headphone body
120R r i g h t - s i d e headphone body
121 d i g i t a l f i l t e r portion
122 D/A converter
123 amplifier c i r c u i t
130 speaker array
131 speaker u n i t
140L, 140R closed curved surface
150 ear pad
150a c i r c u l a r end portion
- 18 -
160 sound pressure signal output portion

[Claim 11
A mounting type device comprising:
a speaker array formed of a plurality of speaker units
I
arranged to surround an auricle,
wherein the speaker ' array is capable of reproducing a
sound field .inside a closed curved surface which is
substantially parallel with the auricle surface in the
vicinity of the auricle using a wave field synthesis.
[Claim 21
The mounting type device according to claim 1,
wherein the speaker array has a closed space in the
normal direction with respect to the auricle surface and is
formed of the plurality of the speaker units which are
arranged to surround the auricle.
[Claim 31
The mounting type device according to claim 2,
wherein the plurality of the speaker vnits of the speaker
array are provided to surround a peripheral edge of the closed
curved surface that is a reproduction surface of the sound
field.
[Claim 41
The mounting type device according to claim 3,
wherein the plurality of the speaker units of the speaker
is able to be reproduced.
[Claim 51
The mounting type device according to claim 4,
whe,rein the plurality of the speaker units of the speaker
I
, array are arranged to be inclined inwardly towards the closed
curved surface.
[Claim 61
The mounting type device according to claim 5, further
comprising:
a donut-shaped ear pad having an opening portion in which
the auricle is able to be inserted, and
wherein the plurality of the speaker units of the speaker
array are arranged along a circular end portion which is
opposite to an abutting side of a listener of the ear pad.
[Claim 71
The mounting type device according to claim 2,
wherein the plurality of the speaker units of the speaker
array are arranged having a distance in which a frequency band
up to a reproduction maximum frequency is able to be
reproduced without receiving the influence of the spatial
aliasing.
[Claim 81
The mounting type device according to claim 7, m wherein a distance Ad [m] of the plurality of the speaker
units of the speaker array satisfies the following formula,
when the reproduction maximum frequency is fmax [Hz] and a
sound velocity is c [m/s],
Ad < c/ (2.fmax).
[Claim 91
The mounting type device according to claim 2,
wherein the closed curved surface is a region having a
diameter ctf 8 to 10 cm around the external auditory meatus
when viewed from a side head portion.
[Claim 101
The mounting type device according to claim 2,
wherein the plurality of the speaker units of the speaker
array are driven by a sound pressure signal for emitting the
sound in a position corresponding to an arrangement position
of each of the speaker units so that the sound field inside
the closed curved surface is able to be reproduced.
[Claim 111
The mounting type device according to claim 10,
%.
wherein the position corresponding to the arrangement
position is a position which is less likely to receive the
influence of the spatial aliasing.
[Claim 121
The mounting type device according to claim 11,
(I 7
wherein the position corresponding to the arrangement
position is a position in the inner side from the arrangement
position of the speaker units.
[Claim 131
A method for reproducing a sound field comprising:
arranging a plurality of speaker units to surround an
auricle,
supplying a sound pressure signal corresponding to each
of the speaker units to the plurality of the speaker units,
and
reproducing the sound field inside a closed curved
surface which is substantially parallel with the auricle
surface in the vicinity of the auricle using a wave field
synthesis.
[Claim 141
A sound pressure signal supplying device comprising:
a sound pressure signal obtaining portion which obtains
sound pressure signals corresponding to a plurality of speaker
units arranged to surround an auricle, and
a sound pressure signal supply portion- which carries out
a filter process in a plurality of the obtained sound pressure
signals for controlling a region and/or for correcting
characteristics of the speaker units, and then supplies the
sound pressure signals to the plurality of the speaker units
respectively.
@ [Claim 151
The sound pressure signal supplying device according to
claim 14,
I
I
wherein the sound pressure signal supply portion carries
I
I out the filter process in the plurality of the sound pressure
I
signals so that the sound emitted from each of speaker units
is allowed to be a sound of a position in the inner side from
the position of eac,h of the speaker units.
[Claim 161
A method for supplying a sound pressure signal
comprising:
obtaining a sound pressure signal corresponding to a
plurality of speaker units arranged to surround an auricle,
and
carrying out a filter process in a plurality of the
obtained sound pressure signals for controlling a region
and/or for correcting characteristics of the speaker units,
and then supplying the sound pressure signals to the plurality
of the speaker units respectively.
[Claim 171
A program for causing a computer to execute a method for
supplying a sound pressure signal including:
obtaining sound pressure signals corresponding to a
plurality of speaker units which are arranged to surround an
auricle, and
and/or for correcting characteristics of the speaker units,
and then supplying the sound pressure signals to the plurality
of the speaker units respectively.
[Claim 181
A computer readable recording medium which records a
program for causing a computer to execute a method for
supplying a sound pressure signal including:
obtaining sound pressure signals corresponding to a
plurality of speaker units which are arranged to surround an
auricle,, and
carrying out a filter process in a plurality of the
obtained sound pressure signals for controlling a region
and/or for correcting characteristics of the speaker units,
and then supplying the sound pressure signals to the plurality
of the speaker units respectively.
[Claim 191
A sound system comprising:
a speaker array which is formed of a plurality of speaker
units arranged to surround an auricle,
a sound pressure signal obtaining portion which obtains
sound pressure signals corresponding to a plurality of the
speaker units of the speaker array, and
a sound pressure signal supply portion which carries out
a filter process in a plurality of the obtained sound pressure
signals for controlling a region and/or for correcting Y
characteristics of the speaker units, and then supplies the
sound pressure signals to the plurality of the speaker units
respectively.
Dated this 15.04.2013
[SHRIMANT 9 SINGH]
OF REMFRY 1 SAGAR
ATTORNEY FOR THE APPLICANT[S]