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JP2010172000

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DESCRIPTION JP2010172000
An object of the present invention is to improve the accuracy of design and control of a sound
field, in a case where a sound field is synthesized by a plurality of speakers and sound is emitted
so as to pop out by bringing a virtual point sound source close to a listening area. Make it
possible to realize the sound field easily and reliably. SOLUTION: A control line S4 is set at a
position close to the speakers SP1, SP2 ... SPm in front of the speakers SP1, SP2 ... SPm, and a
plurality of control points are set on the control line S4, and the control lines The virtual point
sound source 10 is set on the opposite side to the speakers SP1, SP2... SPm side of S4, and a line
parallel to the control line S4 including the point of the virtual point sound source 10 is taken as
the listening side boundary S5. An area on the listener 7 side of the boundary S5 is an area for
synthesizing a sound field. [Selected figure] Figure 1
Sound synthesis device
[0001]
The present invention relates to an apparatus for synthesizing a sound field by a plurality of
speakers to reproduce sound.
[0002]
Aside from multi-channel reproduction such as stereo reproduction, it has been considered to
synthesize sound fields by a plurality of speakers to reproduce sound.
[0003]
For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2004-172786), when a
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sound field is formed by a speaker array, a plurality of audio signals are supplied to expand the
range in which appropriate sound image localization can be obtained. The output of the digital
filter is supplied to a plurality of speakers constituting the speaker array, and a predetermined
delay time is set in each digital filter to form a sound field in the closed space, and output from
the plurality of speakers It is shown that the sound is reflected by the wall of the closed space
and then focused on the position of the listener in the sound field.
[0004]
As a method of controlling the sound field in a three-dimensional space, for example, Non-Patent
Document 1 (Waseda University Research Center for Science and Engineering, Acoustics
Information Processing Laboratory, Yoshio Yamazaki, "Study on three-dimensional virtual reality
based on Kirchhoff integral equation") As shown in), there is a method of using the Kirchhoff
integral formula as follows.
[0005]
That is, assuming a closed surface S including no sound source as shown in FIG. 8, the sound
field in the closed surface S can be expressed by Kirchhoff's integral formula.
In FIG. 8, p (ri) is the sound pressure at point ri in the closed surface S, p (rj) is the sound
pressure at the point rj on the closed surface S, n is the normal at the point rj, and un (rj) is the
modulus The particle velocity in the direction of line n, | ri-rj |, is the distance between point ri
and point rj.
[0006]
The Kirchhoff integral formula is expressed by the equation (1) in FIG. 9, and if the sound
pressure p (rj) on the closed surface S and the particle velocity un (rj) in the direction of the
normal n can be completely controlled, the closed surface S It means that the sound field inside
can be reproduced completely.
[0007]
In equation (1), ω is an angular frequency represented by ω = 2πf, where 音 声 is the density of
air, and Gij is represented by equation (2) in FIG. It is
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[0008]
Equation (1) is for a steady sound field, but the same can be said for a transient sound field by
controlling the instantaneous values of the sound pressure p (rj) and the particle velocity un (rj).
[0009]
Thus, in sound field design based on the Kirchhoff's integral formula, it is only necessary to
reproduce the sound pressure p (rj) on the virtual closed surface S and the particle velocity un
(rj), but practically all on the closed surface S Since it is impossible to control the sound pressure
p (rj) and the particle velocity un (rj) at continuous points of, the sound pressure p (rj) and the
particle velocity un ( The closed surface S is discretized on the assumption that r j) is constant.
[0010]
When the closed surface S is discretized at N points, the equation (1) in FIG. 9 is represented by
the equation (3) in the same figure, and the sound pressure p (rj) of N points on the closed
surface S and By reproducing the particle velocity un (rj), the sound field in the closed surface S
can be completely reproduced.
[0011]
As a system for reproducing the sound pressure p (rj) of the N points and the particle velocity un
(rj) by M sound sources, a system as shown in FIG. 10 is considered.
[0012]
In this system, audio signals from the signal source 1 are supplied to the speakers 3 through the
filters 2 respectively, and the sound pressure is measured at N points on the boundary surface of
the control area 4.
The particle velocity un (rj) in the normal direction is approximately obtained from the sound
pressure signal by the two-microphone method.
[0013]
At this time, in order to reproduce the sound pressure p (rj) and the particle velocity un (rj) at N
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points, the sound pressure at 2N points should be equal to the original sound field.
This results in the problem of finding a value such that the sound pressure at 2N points is closest
to the original sound field as the transfer function Hi (i = 1 to M) of the filter 2.
[0014]
Therefore, let Cij be the transfer function between sound source i (i = 1 to M) and sound
receiving point j (j = 1 to 2N) in the reproduction sound field, and let Hi be the transfer function
of the filter in front of sound source i. An evaluation function for minimizing the difference
between the reproduced sound field and the original sound field as represented by the equation
(4) in FIG. 9 with Pj as the transfer function between the sound source and the sound receiving
point j in the original sound field. Consider J.
[0015]
In order to obtain the transfer function Hi such that the evaluation function J represented by the
equation (4) is minimized, the equation (5) in FIG. 9 may be solved.
[0016]
Furthermore, as an extension to the half space of the Kirchhoff integral formula, as shown in FIG.
11, the sound source 5 is disposed in the space on one side (left side of the drawing) of the
boundary surface S1 and in the space on the opposite side (right side of the drawing) Assuming
the listening area 6 not including the sound source, if sound pressure and particle velocity at all
points on the boundary surface S1 or discrete points as described above are controlled by the
Kirchhoff's integral formula, the sound source can be A desired sound field can be realized in the
listening area 6 which is not included.
[0017]
Specifically, as shown in FIG. 12, a plurality of speakers SP1, SP2... SPm are arranged on the left
side (one side) of a control line (boundary line) S2 of a finite length, and a plurality of controls
are arranged on control line S2. The right side (speaker SP1, SP2... SPm side of the control line S2
by setting points C1, C2... Ck and controlling the sound pressure (amplitude) and phase at each
control point C1, C2. Listener 7 can hear the sound from the speakers SP1, SP2... SPm as the
sound from the virtual point sound source 8 on the left side (speaker SP1, SP2... SPm side) of the
control line S2 Let's do it.
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[0018]
Unexamined-Japanese-Patent No. 2004-172786
[0019]
Waseda University Research Center for Science and Technology, Acoustics Information
Processing Laboratory, Yoshio Yamazaki, "Study on 3D Virtual Reality Based on Kirchhoff
Integral Equation", [online], April 1997, [August 27, 2004 Search ], Internet <URL: http:
www.coust.rise.waseda.ac.jp/publications/happyou/1997-h9.html>
[0020]
However, the virtual point sound source 9 is not located far from the listener 7 on the left side of
the control line S2 (speakers SP1, SP2... SPm side) like the virtual point sound source 8 in FIG. As
shown on the right side of the control line S2 (speaker SP1, SP2. ... on the opposite side to the
SPm side), set at a position close to the listener 7 so that sound sounds like it pops out from the
vicinity of the listener 7 There is a case.
[0021]
However, if this is done, the sound source will be included in the listening area, and the sound
field can not be expressed by the Kirchhoff's integral formula.
[0022]
In this case, considering the sounds Ab and Af from the virtual point sound source 9, the sound
Ab propagating from the virtual point sound source 9 to the control line S2 as shown in FIG. 14
is a sound from the speakers SP1, SP2. As the propagation direction is different from As, it can
not be expressed, nor is it necessary sound.
On the other hand, the sound Af transmitted from the virtual point sound source 9 to the listener
7 as shown in FIG. 15 is a necessary sound.
[0023]
However, as shown in FIG. 15, when the control line S2 is located on the left side of the virtual
point sound source 9 (speakers SP1, SP2... SPm side) and the sound source is included in the
listening area, the sound is calculated by the Kirchhoff integral formula as described above. I can
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not express the place.
[0024]
Therefore, as shown in FIG. 16, a control line S3 for setting each control point C1, C2... Ck is
disposed at a position far away from the speakers SP1, SP2. It is conceivable to set the virtual
point sound source 9 on the left side (speakers SP1, SP2... SPm side) of the control line S3 and set
the right side (listener 7 side) of the control line S3 as a listening area.
[0025]
According to this, since the virtual point sound source 9 is at a position close to the listener 7,
the sound can be heard to pop out, and since the sound source is not included in the listening
area, the sound field is expressed by the Kirchhoff integral formula It becomes possible.
[0026]
However, when control line S3 is set at a position far away from speakers SP1, SP2 ... SPm as
shown in FIG. 16, control line S2 is placed at a position close to speakers SP1, SP2 ... SPm as
shown in FIG. As compared with the setting, the accuracy of the design and control of the sound
field is degraded, and it becomes difficult to realize the desired sound field easily and reliably.
[0027]
That is, when the control line S2 is set at a position close to the speakers SP1, SP2... SPm as
shown in FIG. 12, the sound waves reaching the control point C1 from the speakers SP1, SP2.
Since there is a large sound pressure difference and phase difference between the sound waves
from the speakers SP1, SP2 .... SPm to the same control point on the control line S2, the accuracy
of the design and control of the sound field is improved, A desired sound field can be realized
easily and reliably.
[0028]
On the other hand, when the control line S3 is set at a position far away from the speakers SP1,
SP2... SPm as shown in FIG. 16, the control point C1 is reached from each of the speakers SP1,
SP2. Since the sound pressure difference and phase difference between the sound waves
reaching the same control point on the control line S3 from each of the speakers SP1, SP2. It
becomes difficult to realize the desired sound field easily and reliably.
[0029]
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Therefore, the present invention improves the accuracy of the sound field design and control
when the virtual point sound source sounds close to the listening area so that the sound can be
heard as popping out, and a desired sound field can be realized easily and reliably. It is
something that can be done.
[0030]
To solve the above problems, according to one aspect of the present invention, there is provided
a speaker array comprising a plurality of speakers, and a plurality of filters provided in front of
each of the speakers, to which the same audio signal is supplied. A sound synthesis device is
provided.
The transfer function of each filter sets a control line at a position close to each speaker at the
front position of each speaker, sets a plurality of control points on the control line, and the
speakers of the control line A virtual point sound source is set on the side opposite to the side,
and a region including the virtual point sound source and having a line parallel to the control line
as a listening side boundary, a region on the side opposite to the control line side of the listening
side boundary A transfer function for realizing a first sound field in which sound fields are
synthesized, a control line is set at a position close to each speaker at a position in front of each
speaker, and a plurality of controls on the control line A point is set, and a virtual point sound
source is set on the speaker side of the control line to select a transfer function for realizing a
second sound field.
[0031]
As described above, according to the present invention, when the virtual point sound source is
brought close to the listening area so that the sound can be heard as if it pops out, the accuracy
of the design and control of the sound field is improved, and the desired sound field is obtained.
It can be realized easily and reliably.
[0032]
It is a figure which shows an example of the sound synthesis apparatus of this invention.
It is a figure where it uses for description of the sound field design method of this invention.
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It is a figure where it uses for description of the sound field design method of this invention.
It is a figure where it uses for description of the sound field design method of this invention.
It is a figure where it uses for description of the sound field design method of this invention.
It is a figure which shows the model of simulation.
It is a figure which shows the fingerprint of a simulation result.
It is a figure which shows the sound field in the virtual closed surface which does not contain a
sound source.
It is a figure which shows the Kirchhoff integral formula.
FIG. 2 shows a system that reproduces the sound pressure and particle velocity of N points by M
sound sources.
It is a figure which shows the principle of extension to the half space of the Kirchhoff's integral
formula.
It is a figure which shows the example of expansion to the half space of the Kirchhoff's integral
formula.
It is a figure which shows the case where a virtual point sound source is set to the opposite side
to the speaker side of a control line.
It is a figure which shows the sound propagated to the control line side from a virtual point
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sound source.
It is a figure which shows the sound propagated to a listener side from a virtual point sound
source.
It is a figure which shows the case where a control point is set to the position near a listener.
It is a figure which shows the sound wave which reaches a control point from each speaker in the
case of setting a control point in the position near a speaker.
It is a figure which shows the sound wave which arrives at a control point from each speaker in
the case of setting a control point in the position which left | separated from the speaker greatly.
[0033]
FIG. 1 shows an example of the sound synthesis system of the present invention, which
reproduces sound by forming a sound field designed by a sound field design method described
later.
[0034]
The digital audio signal source 100 reads non-compressed PCM (Pulse Code Modulation) audio
data from a recording medium such as a compact disk or hard disk, or ATRAC (a registered
trademark, which is an abbreviation of Adaptive Transform Acoustic Coding) or MP3. It reads out
and decompresses audio data compressed by (MPEG-1 Audio Layer-3) or the like, or receives
uncompressed PCM audio data by a broadcast signal or network, or ATRAC (registered
trademark) or MP3 etc. It receives and decompresses audio data compressed by the.
[0035]
The audio data from the digital audio signal source 100 is supplied to a plurality of digital filters
201, 202.
The transfer functions of the digital filters 201, 202,... 20 m are calculated and determined by a
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sound field design method described later.
[0036]
The audio data of the output of the digital filter 201, 202 ... 20m is converted to an analog audio
signal by the DA converter 301, 302 ... 30m, and the converted audio signal is converted by the
audio amplifier circuits 401, 402 ... 40m, respectively. The signal is amplified and supplied to the
speakers SP1, SP2... SPm.
The speakers SP1, SP2... SPm are configured as a speaker array.
[0037]
The arithmetic processing unit 500 is configured as a computer unit including a CPU, a ROM,
and a RAM (not shown), and sets filter coefficients of the digital filters 201, 202,.
[0038]
Furthermore, in this example, the arithmetic processing unit 500 is also used for sound field
design by a sound field design method described later.
For that purpose, the storage unit 600 and the key input unit 700 are connected to the
arithmetic processing unit 500.
The storage unit 600 stores the filter coefficients of the digital filters 201, 202... 20 m as data of
the result of the sound field design, and the key input unit 700 inputs the conditions of the sound
field design. And other necessary operations.
[0039]
In the sound field design method of the present invention, as shown in FIG. 1, a control line S4 is
set at a position close to the speakers SP1, SP2 ... SPm in front of (in front of) the speakers SP1,
SP2. A plurality of control points are set on S4, and the virtual point sound source 10 is set on
the opposite side (right side in the figure) of the speakers SP1, SP2... SPm side of the control line
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S4. A line parallel to the control line S4 including the above is taken as the listening-side
boundary S5, and the area on the listener 7 side (the right side in the figure) of the listening-side
boundary S5 is taken as an area for synthesizing the sound field.
[0040]
That is, by setting the virtual point sound source 10 between the control line S4 at a position
close to the speakers SP1, SP2 .... SPm and the listener 7, as shown in FIG. 2, the right side
(listener 7 side) of the control line S4. The area Ec of can be an area for synthesizing the sound
field.
[0041]
However, in this case, as shown in FIG. 3, a line parallel to the control line S4 including the point
x0 of the virtual point sound source is the listening side boundary S5, and the area Ez on the
right side (listener 7 side) of the listening side boundary S5. Is an area for synthesizing an actual
sound field.
[0042]
The synthetic sound field of FIG. 2 and the synthetic sound field of FIG. 3 also look the same from
the listener 7, but by setting as shown in FIG. 3, the condition of Kirchhoff's integral formula is
satisfied, and the control line by Kirchhoff's integral formula The sound field by the virtual point
sound source at the point x0 on the right side (listener 7 side) of the control line S4 is controlled
by controlling the sound pressure and the phase at each control point x1, x2, x3. It can be
realized on the right side (listener 7 side) of the listener-side boundary S5 including the above.
[0043]
In this case, the sound propagating from the point x0 of the virtual point sound source to the
right (the listener 7 side) as shown by the arrow in FIG. 3 can be described by the left side
(speaker side) of the point x0 of the virtual point sound source.
[0044]
Specifically, as the sound pressure (amplitude) and phase at each control point x1, x2, x3... On
the control line S4, for example, as shown in FIG. Is larger than the signals S (x1) and S (x3) at the
control points x1 and x3 as the signal S (x2) at the control point x2, and as the phase, the signals
S (x1) and S (x) at the control points x1 and x3 x3) is expressed as being ahead of the signal S
(x2) at the control point x2.
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[0045]
When considered on the frequency axis, in the case of an ideal point sound source, the sound
pressure (amplitude) and phase at each control point are the distance r from the virtual point
sound source to the control point and the frequency f of the audio signal. When it is assumed
that the virtual point sound source 10 is the right side (listener side) of the control line S4 as
described above, R (in the listener's side) of the equation (7) It is sufficient to take the complex
conjugate of r, f) and reverse the time axis.
Alternatively, the positive and negative of the time axis may be reversed directly on the time axis,
and the past and the future may be reversed.
[0046]
We performed computer simulation of sound field design (sound field formation) by the above
sound field design method.
The model is shown in FIG.
[0047]
In this simulation model, the speaker SP is 0.1 m (10 cm) centered on the position of the origin
(0, 0) as indicated by a white circle on the x axis of the xy plane (the numerical value of xy
coordinates is meters). 28 pieces in total at the left and right sides, 28 pieces in total), and the
control line S4 at the position of y = −0.1 m in front of the speaker SP (listener side), the same as
the array of the speaker SP 2.7 m Set over the length of the control line S4 and set a number of
control points on the control line S4.
The virtual point sound source 10 was set at the position of x = 0 m and y = -1 m.
The audio signal was a sine wave of 1 kHz.
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[0048]
FIG. 7 shows the simulation results of the above-described model, and shows the ripples of the
sound wave in the shaded area in FIG.
As apparent from the above, it is possible to form a desired sound field in an area in front of the
virtual point sound source 10 (listener side) by the above-described sound field design method.
[0049]
As the sound generating apparatus shown in FIG. 1, the control line S4 is set at a position close to
the speakers SP1, SP2... SPm in advance and as shown in FIG. 1 and FIG. As shown in FIG. 12, the
filter line (transfer function) forming the sound field when the point sound source 10 is set at a
position close to the listener 7 and the control line S2 at a position close to the speakers SP1,
SP2. A filter coefficient (transfer function) for forming a sound field in the case of setting and
setting the virtual point sound source 8 to the speakers SP1, SP2... SPm is prepared and written
in the storage unit 600 and stored by the user. By selecting one of the modes by the operation at
key input unit 700, the filter coefficient (transfer function) corresponding to the selected mode
becomes digital filter 201. 202 may be configured to be loaded into ‥‥ 20 m.
[0050]
According to this, according to the case, the user can select the sound from the mode in which
the sound is heard to pop out from the vicinity of the user or the normal mode to be heard as the
sound from the point in the vicinity of the speaker. Can play and listen.
[0051]
The main parts are all described in the figure, so they are omitted here.
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