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JP2013172236

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DESCRIPTION JP2013172236
Abstract: The present invention provides a sound field sound collecting and reproducing
technology capable of reproducing a sound field even if the directivity of the speakers
constituting the speaker array is any directivity. A filter F to (ω) defined by the following
equation is applied to a space-time frequency domain signal P to (ω) generated by a conversion
filter unit 3 based on a signal collected by a microphone array. Apply to generate filtered signal D
~ (ω). The spatial frequency inverse transform unit 4 transforms the filtered signal D ~ (ω) into a
frequency domain signal by inverse Fourier transform of space. The frequency inverse transform
unit 5 transforms the frequency domain signal into a time domain signal by inverse Fourier
transform. [Selected figure] Figure 1
Sound field sound collecting and reproducing apparatus, method and program
[0001]
The present invention relates to a wave field synthesis technique in which a sound signal is
collected by a microphone array installed in a certain sound field, and the sound field is
reproduced by a speaker array using the sound signal.
[0002]
For example, Non-Patent Document 1 describes a wave field synthesis technique in which a
microphone array installed in a certain sound field picks up a signal and uses that signal to
reproduce the sound field with a speaker array. Technology is known.
[0003]
03-05-2019
1
In the technology described in Non-Patent Document 1, the filters are configured on the premise
that the speakers constituting the speaker array are nondirectional.
[0004]
Shoichi Koyama, 3 others, "Spatio-temporal frequency domain signal conversion method for
sound field collection and reproduction", Proceedings of the Acoustical Society of Japan,
September 2011, P. 635-636
[0005]
However, in the technology described in Non-Patent Document 1, since the filters constituting
the speaker array are non-directional on the premise that the speakers constituting the speaker
array are non-directional, the speakers constituting the speaker array are not non-directional.
Can not apply the technology described in Non-Patent Document 1.
[0006]
An object of the present invention is to provide a sound field sound collecting and reproducing
apparatus, method, and program that can be applied even if the directivity of the speakers
constituting the speaker array is any directivity.
[0007]
In order to solve the above problems, in the sound field collection and reproduction apparatus
according to one aspect of the present invention, the microphone array is disposed on the xz
plane, j is an imaginary unit, ω is a frequency, and c is a speed of sound. , K = ω / c, kx, n is the
wave number in the x-axis direction, n is its index, kz, m is the wave number in the z-axis
direction, m is its index, p, q, s are preset Based on the signals collected by the microphone array
as multipole coefficients dp, q, s obtained by multipolar expansion of the transfer characteristics
of each speaker constituting the speaker array by the order p, q, s A conversion filter unit that
generates a filtered signal D to nm (ω) by applying a filter F to nm (ω) defined by the following
equation to the generated space-time frequency domain signal P to nm (ω) When,
[0008]
[0009]
Space frequency inverse transform unit which converts filtered signal D.about.nm (.omega.) Into
frequency domain signal by inverse Fourier transform of space, frequency inverse transform unit
03-05-2019
2
which converts frequency domain signal into time domain signal by inverse Fourier transform,
,including.
[0010]
In the sound field collection and reproduction apparatus according to one aspect of the present
invention, the microphone array is disposed on the xz plane, j is an imaginary unit, ω is a
frequency, c is a speed of sound, k = ω / c, kx , n is the wave number in the x-axis direction, n is
its index, kz, m is the wave number in the z-axis direction, m is its index, p, q, s is the preset
order, and the speaker array is configured Frequency conversion for converting signals collected
by the microphone array into frequency domain signals by Fourier transform, with dp, q, s being
multipole coefficients obtained by multipole expanding the transfer characteristic of each
speaker in the order p, q, s And a space frequency conversion unit for converting a frequency
domain signal to a space time frequency domain signal P to nm (ω) by Fourier transform of
space, and for the space time frequency domain signal P to nm (ω) Transform filter applying the
defined filter F ~nm (ω) to generate the filtered signal D ~nm (ω) Department and.
[0011]
[0012]
In the sound field collection and reproduction apparatus according to one aspect of the present
invention, the arrangement direction of the microphone arrays arranged in a straight line is the x
axis direction, j is the imaginary unit, ω is the frequency, c is the speed of sound, and k = ω / c,
kx, n is the wave number in the x-axis direction, n is its index, p, q is a preset order, and the
transfer characteristics of each speaker constituting the speaker array are multiplexed by the
order p, q Let the pole-expanded multipole coefficient be dp, q, H 0 <(2)> be the second Hankel
function of n = 0, y ref be the position to match the transfer characteristics, k は be defined by
the following equation,
[0013]
[0014]
Filtered signal D by applying filters F to n (ω) defined by the following equation to space-time
frequency domain signals P to n (ω) generated based on signals collected by the microphone
array a conversion filter unit that generates n n (ω);
03-05-2019
3
[0015]
[0016]
Space frequency inverse transform unit that converts filtered signal D to n (ω) into frequency
domain signal by inverse Fourier transform of space; frequency inverse transform unit that
converts frequency domain signal to time domain signal by inverse Fourier transform; ,including.
[0017]
In the sound field collection and reproduction apparatus according to one aspect of the present
invention, the arrangement direction of the microphone arrays arranged in a straight line is the x
axis direction, j is the imaginary unit, ω is the frequency, c is the speed of sound, and k = ω / c,
kx, n is the wave number in the x-axis direction, n is its index, p, q is a preset order, and the
transfer characteristics of each speaker constituting the speaker array are multiplexed by the
order p, q Let the pole-expanded multipole coefficient be dp, q, H 0 <(2)> be the second Hankel
function of n = 0, y ref be the position to match the transfer characteristics, k は be defined by
the following equation,
[0018]
[0019]
A frequency converter that converts a signal collected by a microphone array into a frequency
domain signal by Fourier transform, and a space frequency transform that converts the
frequency domain signal into space-time frequency domain signal P to n (ω) by Fourier
transform of space And a conversion filter unit that generates a filtered signal D.about. (Ω) by
applying a filter F.about.n (.omega.) Defined by the following equation to the space-time
frequency domain signal P.about.n (.omega.) And.
[0020]
[0021]
By constructing the filter using the transfer characteristic measured in advance, it is possible to
reproduce the sound field even if the directivity of the loudspeakers constituting the loudspeaker
array is any directivity.
03-05-2019
4
[0022]
FIG. 1 is a functional block diagram showing an example of a sound field collection and
reproduction device according to a first embodiment.
FIG. 2 is a view for explaining an example of the arrangement of a microphone array and a
speaker array of the sound field collection and reproduction device according to the first
embodiment.
The flowchart which shows the example of the sound field sound collection reproduction |
regeneration method of 1st embodiment and 2nd embodiment.
The figure for demonstrating the measuring method of order p, q, s, and coefficient dp, q, s.
The functional block diagram which shows the example of the sound field sound collection
reproducing | regenerating apparatus of 2nd embodiment.
The figure for demonstrating the example of arrangement | positioning of the microphone array
of the sound field sound collection reproducing | regenerating apparatus of 2nd embodiment,
and a speaker array.
[0023]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0024]
First Embodiment As shown in FIG. 2, the sound field collection and reproduction apparatus and
method according to the first embodiment includes N ×× Nz microphones arranged at the y = 0
position of the first room. Two-dimensional microphone arrays M1-1, M2-1,..., MNx-Nz, and Nx ×
Nz speakers arranged in the second room. , SNx-Nz, the sound field of the first room formed by
the sound generated by the sound source S is reproduced in the second room.
03-05-2019
5
[0025]
Nx and Nz are arbitrary integers.
In this embodiment, the number of microphones constituting the microphone array M1-1, M2-1,
..., MNx-Nz is the same as the number of speakers constituting the speaker array S1-1, S2-1, ...,
SNx-Nz. It is.
The microphones Mi-j constituting the microphone arrays M1-1, M2-1,..., MNx-Nz are arranged in
a grid on the xz plane of y = 0.
The speakers constituting the speaker arrays S1-1, S2-1,..., SNx-Nz are also arranged in a lattice
on the xz plane.
The sizes of the microphone arrays M1-1, M2-1,..., MNx-Nz and the sizes of the speaker arrays
S1-1, S2-1,.
The positions of the microphones Mi-j in the microphone arrays M1-1, M2-1,..., And MNx-Nz are
the speaker arrays S1-1, S2-1, ... of the speakers Si-j corresponding to the microphones Mi-j. ,
SNx-Nz, but may be different.
If the positions are the same, the sound field can be reproduced more faithfully.
[0026]
Let rs = (xi, 0, zj) represent the positions of the microphones constituting the microphone array
M1-1, M2-1,..., MNx-Nz arranged in the y = 0 plane of the first room Make it
[0027]
As shown in FIG. 1, the sound field sound collecting and reproducing apparatus according to the
first embodiment includes a frequency converter 1, a space frequency converter 2, a conversion
filter 3, a space frequency inverse converter 4, a frequency inverse converter 5, and a window
function. For example, the processing of each step illustrated in FIG. 3 is performed.
03-05-2019
6
[0028]
The microphone arrays M1-1, M2-1,..., MNx-Nz of the first room pick up the sound emitted by
the sound source S of the first room and generate a time domain signal.
The generated signal is sent to the frequency converter 1.
A signal of time t collected in the microphone Mi-j of rs = (xi, 0, zj) is denoted as pij (t).
[0029]
The frequency converter 1 converts the signals pij (t) collected by the microphone arrays M1-1,
M2-1,..., MNx-Nz into frequency domain signals Pij (.omega.) By Fourier transform (step S1).
The generated frequency domain signal P ij (ω) is sent to the spatial frequency converter 2.
ω is a frequency.
For example, frequency domain signal P ij (ω) is generated by short time discrete Fourier
transform.
Of course, the frequency domain signal P ij (ω) may be generated by another existing method.
Alternatively, the frequency domain signal Pij (ω) may be generated using a method such as
overlap ad.
When the input signal is long or when the signal is continuously input as in real time processing,
processing is performed every frame, for example, every 10 ms.
03-05-2019
7
The frequency domain signal P ij (ω) is defined, for example, as follows.
J in the argument of the function exp is an imaginary unit.
[0030]
[0031]
The spatial frequency transform unit 2 transforms the frequency domain signal P ij (ω) into the
space-time frequency domain signal P ~nm (ω) by Fourier transform of space (step S 2).
The space-time frequency domain signal P ~nm (ω) is calculated for each ω.
The converted space-time frequency domain signal P ~nm (ω) is sent to the conversion filter unit
3.
Specifically, the spatial frequency transform unit 2 calculates P to nm (ω) defined by the
following equation (1).
[0032]
[0033]
kx, n is a wave number in the x-axis direction, n is an index of the wave number kx, n, kz, m is a
wave number in the z-axis direction, and m is an index of the wave number kz, m.
The wave number is the so-called spatial frequency or angular spectrum.
03-05-2019
8
The above equation (1) is an example of conversion to the space-time frequency domain, and
Fourier transform of space may be performed by another method.
[0034]
The conversion filter unit 3 applies the filter F to nm (ω) defined by the following equation (2) to
the space-time frequency domain signal P to nm (ω), and the filtered signal D to nm (ω) Are
generated (step S3).
The filtered signal D ~nm (ω) is transmitted to the spatial frequency inverse transform unit 4.
[0035]
[0036]
In Equation (2), p, q, s are preset orders, and dp, q, s are multiplexes obtained by multipole
expansion of the transfer characteristics of the speakers constituting the speaker array by the
orders p, q, s It is a pole coefficient.
For example, any one or more of p, q and s are positive values other than 0, such as setting all of
p, q and s to 1. The reason why the filters F to nm (ω) are expressed by the equation (2) will be
described later.
[0037]
The spatial frequency inverse transform unit 4 transforms the filtered signal D ~nm (ω) into a
frequency domain signal Dij (ω) by inverse Fourier transform of space (step S 4). The converted
frequency domain signal Dij (ω) is sent to the frequency inverse transform unit 5. Specifically,
the spatial frequency inverse transform unit 4 calculates the frequency domain signal Dij (ω)
defined by the following equation (3).
03-05-2019
9
[0038]
[0039]
The frequency inverse transform unit 5 transforms the frequency domain signal Dij (ω) into a
time domain signal P <d> ij (t) by inverse Fourier transform (step S5).
The time domain signal P <d> ij (t) obtained for each frame by the inverse Fourier transform is
appropriately shifted and linearly summed to be a continuous time domain signal. As the inverse
Fourier transform, an existing method such as a short time discrete inverse Fourier transform
may be used. The time domain signal P <d> ij (t) is sent to the window function unit 6.
[0040]
The window function unit 6 multiplies the time domain signal P <d> ij (t) by the window function
to generate a post-window function time domain signal dij (t) (step S6). The post-window
function time domain signal dij (t) is sent to the speaker arrays S1-1, S2-1,..., SNx-Nz.
[0041]
For example, a so-called Tukey window function wij defined by the following equation is used as
a window function. Ntpr is a score to which a taper is applied, and is an integer of 1 or more and
Nx and Nz or less. Of course, other window functions may be used.
[0042]
[0043]
The speaker arrays S1-1, S2-1,..., SNx-Nz reproduce sound based on the window function after
time domain signal dij (t).
03-05-2019
10
Specifically, the speaker Si-j reproduces the sound based on the time-domain signal after the
window function dij (t) as i = 1,..., Nx, j = 1,. Thereby, the wave front at the position y = 0 of the
first room is reproduced by the speaker arrays S1-1, S2-1,..., SNx-Nz of the second room, and the
sound field of the first room is It can be reproduced in two rooms.
[0044]
If the number of microphones constituting the microphone array is larger than the number of
speakers constituting the speaker array, the time-domain signal dij (t) may be thinned after the
window function. On the other hand, when the number of microphones constituting the
microphone array is smaller than the number of speakers constituting the speaker array, the
interpolation may be performed by averaging the time domain signal dij (t) after the window
function. .
[0045]
Hereinafter, the reason why the filter F to nm (ω) is expressed as the above equation (2) will be
described.
[0046]
The position vector of the reproduction area is r = (x, y, z), and the position vector of the
secondary sound source plane is r0 = (x0, 0, z0).
Assuming that the sound pressure distribution of the frequency ω in the reproduction region is P
(r, ω) and the drive signal of the secondary sound source is D (r0, ω), the following relational
expression can be written.
[0047]
[0048]
03-05-2019
11
Here, Gsp (r−r0, ω) is a transfer function between r and r0.
Fourier transform of space in the x-axis direction and z-axis direction of equation (4) gives the
following.
[0049]
[0050]
Here, kx and kz represent the spatial frequency in the x-axis direction and the spatial frequency
in the z-axis direction, respectively.
Moreover, the spatial frequency domain is shown by "<->". Here, the Fourier transform of space is
defined as follows.
[0051]
[0052]
G <<> sp (r, ω) is a transfer characteristic having arbitrary pointing specification, but can be
expressed as follows using a multipole expansion.
[0053]
[0054]
Here, r was as follows.
[0055]
[0056]
03-05-2019
12
また、
[0057]
[0058]
であり、
[0059]
[0060]
である。
Next, the first kind of Rayleigh integration is introduced as an ideal sound field.
[0061]
[0062]
Here, G (r−r 0, ω) is a three-dimensional free space Green's function.
[0063]
[0064]
Here, k = ω / c is the wave number and c is the speed of sound.
When this equation is subjected to space Fourier transform, the following equation is obtained.
03-05-2019
13
[0065]
[0066]
また、
[0067]
[0068]
である。
By the equations (5) and (7), the drive signal of the secondary sound source is obtained as
follows.
[0069]
[0070]
At this time, since the orders p, q, s of the multipole expansion and the coefficients dp, q, s are
unknown, they need to be acquired by measuring the speaker characteristics.
[0071]
In the measurement of the speaker characteristics, the impulse response may be measured on a
spherical surface equidistant from the speaker as shown in FIG.
In order to obtain the coefficients of multipole expansion using the obtained impulse response,
the least squares fitting to Equation (6) may be performed at each frequency.
The orders p, q and s are truncated at an appropriate order.
03-05-2019
14
Alternatively, a spherical harmonic spectrum may be obtained and converted into an order of
multipole expansion.
At this time, since only one characteristic is required in the filter equation, some speaker
characteristics may be measured and their average may be taken.
[0072]
As described above, by constructing the filter using the transfer characteristic measured in
advance, it is possible to reproduce the sound field even if the directivity of the speaker
constituting the speaker array is any directivity.
[0073]
Second Embodiment As shown in FIG. 6, in the sound field collection and reproduction apparatus
and method of the second embodiment, Nx linearly arranged at the position of y = 0, z = 0 in the
first room One-dimensional microphone arrays S1, S2,..., SNx consisting of one-dimensional
microphone arrays M1, M2,..., MNx consisting of individual microphones and Nx speakers
arranged linearly in the second room And the sound field of the first room formed by the sound
generated by the sound source S is reproduced in the second room.
Compared to the first embodiment, the number of microphones, the number of speakers, and the
number of channels can be reduced, which makes the implementation relatively easy.
[0074]
Nx is an arbitrary integer.
In this embodiment, the number of microphones configuring the microphone arrays M1, M2,...,
MNx is the same as the number of speakers configuring the speaker arrays S1, S2,.
The microphones Mi constituting the microphone arrays M1, M2,..., MNx are arranged at equal
03-05-2019
15
intervals.
Further, the speakers constituting the speaker arrays S1, S2,..., SNx are also arranged at equal
intervals.
The size of the microphone arrays M1, M2,..., MNx and the size of the speaker arrays S1, S2,.
It is preferable that the positions of the microphones Mi in the microphone arrays M1, M2, ...,
MNx are the same as the positions in the speaker arrays S1, S2, ..., SNx of the speakers Si
corresponding to the respective microphones Mi. Also good.
If the positions are the same, the sound field can be reproduced more faithfully.
[0075]
The positions of the microphones constituting the microphone arrays M1, M2,..., MNx arranged
at the y = 0, z = 0 positions of the first room are represented by rs = (xi, 0, 0).
[0076]
The sound field sound collecting and reproducing apparatus according to the second
embodiment includes, as shown in FIG. For example, the processing of each step illustrated in
FIG. 3 is performed.
[0077]
The microphone arrays M1, M2,..., MNx arranged at the y = 0, z = 0 positions of the first room
pick up the sound emitted by the sound source S of the first room and generate a time domain
signal. Generate
The generated signal is sent to the frequency converter 1.
The signal of time t collected in the microphone Mi of rs = (xi, 0, 0) is denoted as pi (t).
03-05-2019
16
[0078]
The frequency converter 1 converts the signal pi (t) collected by the microphone arrays M1,
M2,..., MNx into a frequency domain signal Pi (ω) by Fourier transformation (step S1).
The generated frequency domain signal Pi (ω) is sent to the spatial frequency converter 2.
ω is a frequency.
For example, the frequency domain signal Pi (ω) is generated by short time discrete Fourier
transform.
Of course, the frequency domain signal Pi (ω) may be generated by another existing method.
Alternatively, the frequency domain signal Pij (ω) may be generated using a method such as
overlap ad. When the input signal is long or when the signal is continuously input as in real time
processing, processing is performed every frame, for example, every 10 ms. The frequency
domain signal Pi (ω) is defined, for example, as follows. J in the argument of the function exp is
an imaginary unit.
[0079]
[0080]
The spatial frequency transform unit 2 transforms the frequency domain signal Pi (ω) into the
space-time frequency domain signal P ~n (ω) by Fourier transform of space (step S 2).
The space-time frequency domain signals P ~n (ω) are calculated for each ω. The converted
space-time frequency domain signals P to n (ω) are sent to the conversion filter unit 3.
Specifically, the spatial frequency transform unit 2 calculates P to n (ω) defined by the following
equation (7).
03-05-2019
17
[0081]
[0082]
kx, n is a wave number in the x-axis direction, and n is an index of the wave number kx, n.
The wave number is the so-called spatial frequency or angular spectrum. The above equation (7)
is an example of transformation to the space-time frequency domain, and Fourier transform of
space may be performed by another method.
[0083]
The conversion filter unit 3 applies the filter F to n (ω) defined by the following equation to the
space-time frequency domain signal P to n (ω) to generate a post-filtering signal D to n (ω) (Step
S3). The post-filtering signals D to n (ω) are transmitted to the spatial frequency inverse
transform unit 4. The reason why the filters F to nm (ω) are expressed by the equation (8) will
be described later.
[0084]
[0085]
In equation (8), p and q are pre-set orders, and dp and q are multipole coefficients obtained by
multipole expansion of the transfer characteristics of the speakers constituting the speaker array
with the orders p and q.
For example, one or more of p and q are positive non-zero values, such as setting all of p and q to
1. y ref is a position at which the transfer characteristics are matched. More specifically, as
shown in FIG. 6, yref represents the distance between the speaker array S1, S2,..., SNx and the
linear position where the amplitude of the signal to be reproduced is adjusted. H0 <(2)> is a
03-05-2019
18
second Hankel function of n = 0, and kρ is defined by the following equation.
[0086]
[0087]
The spatial frequency inverse transform unit 4 transforms the post-filtering signals D to n (ω)
into a frequency domain signal Di (ω) by inverse Fourier transform of space (step S 4).
The converted frequency domain signal Di (ω) is sent to the frequency inverse transform unit 5.
Specifically, the spatial frequency inverse transform unit 4 calculates a frequency domain signal
Di (ω) defined by the following equation (9).
[0088]
[0089]
The frequency inverse transform unit 5 transforms the frequency domain signal Di (ω) into a
time domain signal P <d> i (t) by inverse Fourier transform (step S5).
The time domain signal P <d> i (t) obtained for each frame by the inverse Fourier transform is
appropriately shifted and linearly summed to be a continuous time domain signal. As the inverse
Fourier transform, an existing method such as a short time discrete inverse Fourier transform
may be used. The time domain signal P <d> i (t) is sent to the window function unit 6.
[0090]
The window function unit 6 multiplies the time domain signal P <d> i (t) by the window function
to generate a post-window function time domain signal di (t) (step S6). The post-window function
time domain signal di (t) is sent to the loudspeaker arrays S1, S2, ..., SNx.
03-05-2019
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[0091]
For example, a so-called Tukey window function wi defined by the following equation is used as a
window function. Ntpr is a score to which a taper is applied, and is an integer of 1 or more and
Nx or less. Of course, other window functions may be used.
[0092]
[0093]
The speaker arrays S1, S2,..., SNx reproduce sound based on the window function after time
domain signal di (t).
Specifically, the speaker Si reproduces a sound based on the window function after time domain
signal di (t) as i = 1,..., Nx.
[0094]
Thereby, the wave front at the position y = 0 of the first room is reproduced by the speaker
arrays S1, S2, ..., SNx of the second room, and the sound field of the first room is reproduced in
the second room be able to.
[0095]
At this time, the amplitudes of the reproduced signals match at the position on the straight line
represented by yref.
Specifically, as shown in FIG. 6, the speaker array S1, S2,..., SNx has the same height, and is
spaced from the speaker array S1, S2,. The amplitudes coincide at positions on a straight line
parallel to the straight line where S2, ..., SNx are arranged.
03-05-2019
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[0096]
When the number of microphones constituting the microphone array is larger than the number
of speakers constituting the speaker array, the time-domain signal di (t) may be thinned after the
window function. On the other hand, when the number of microphones constituting the
microphone array is smaller than the number of speakers constituting the speaker array,
interpolation may be performed by averaging the time domain signal di (t) after the window
function. .
[0097]
Hereinafter, the reason why the filters F to n (ω) are expressed as the above equation (8) will be
described.
[0098]
Consider reproducing only on the xy plane using a linear array.
The position vector of the reproduction region is r = (x, y, 0), and the position vector of the
secondary sound source plane is r0 = (x 0, 0, 0). Assuming that the sound pressure distribution of
the frequency ω in the reproduction region is P (r, ω) and the drive signal of the secondary
sound source is D (r0, ω), the following relational expression can be written.
[0099]
[0100]
Here, Gsp (r−r0, ω) is a transfer function between r and r0.
Fourier transform of space in the x-axis direction of equation (10) gives the following.
[0101]
03-05-2019
21
[0102]
Here, kx represents the spatial frequency in the x-axis direction.
Moreover, the spatial frequency domain is shown by "<->". Here, the Fourier transform of space is
defined as follows.
[0103]
[0104]
As in the case of the planar array, G <-> sp (r, ω) can be expressed as follows using multipole
expansion.
[0105]
[0106]
H0 <(2)> is a second Hankel function of n = 0.
The second Hankel function Hn <(2)> is defined as follows using the first Bessel function Jn (x)
and the second Bessel function Yn (x).
[0107]
[0108]
Next, we introduce a two-dimensional first-class Rayleigh integral.
[0109]
03-05-2019
22
[0110]
ここで、
[0111]
[0112]
である。
k = ω / c is the wave number and c is the speed of sound.
[0113]
By applying equation (13) to space Fourier transform, the following equation is obtained.
[0114]
[0115]
ここで、
[0116]
[0117]
である。
また、
03-05-2019
23
[0118]
[0119]
である。
Therefore, the drive signal of the secondary sound source is obtained as follows.
[0120]
[0121]
At this time, since the orders p and q of the multipole expansion and the coefficients dp and q are
unknown, they need to be acquired by measuring the speaker characteristics as in the case of the
planar array.
[0122]
In the measurement of the speaker characteristics, as in the case of the planar array, the impulse
response may be measured on a spherical surface equidistant to the speaker as shown in FIG.
In order to obtain the coefficients of multipole expansion using the obtained impulse response,
the least squares fitting to Equation (12) may be performed at each frequency.
The orders p and q are truncated at an appropriate order.
Alternatively, a spherical harmonic spectrum may be obtained and converted into an order of
multipole expansion.
At this time, since only one characteristic is required in the filter equation, some speaker
characteristics may be measured and their average may be taken.
03-05-2019
24
[0123]
As described above, by constructing the filter using the transfer characteristic measured in
advance, it is possible to reproduce the sound field even if the directivity of the speaker
constituting the speaker array is any directivity.
[0124]
[Modifications, etc.] In the first embodiment, the microphone arrays M1-1, M2-1, ..., MNx-Nz and
the speaker arrays S1-1, S2-1, ..., SNx-Nz are not arranged in a straight line. It does not have to be
on the plane if it is.
[0125]
The number of microphones constituting the microphone array may be different from the
number of speakers constituting the speaker array.
If the number of microphones constituting the microphone array is larger than the number of
speakers constituting the speaker array, the output signals of the speakers may be thinned out.
On the other hand, when the number of speakers constituting the speaker array is larger than the
number of microphones constituting the microphone array, interpolation may be performed such
as averaging the output signals of the speakers.
[0126]
Each part constituting the sound field sound collecting and reproducing apparatus may be
provided in either the sound collecting apparatus arranged in the first room or the reproducing
apparatus arranged in the second room.
In other words, processing of each of the frequency conversion unit 1, the space frequency
conversion unit 2, the conversion filter unit 3, the space frequency inverse conversion unit 4, the
frequency inverse conversion unit 5, and the window function unit 6 is arranged in the first room
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It may be performed by the sound collection apparatus, or may be performed by the
reproduction apparatus arranged in the second room.
The signal generated by the sound collection device is transmitted to the reproduction device.
[0127]
The positions of the first room and the second room are not limited to those shown in FIGS. 2
and 6.
The first room and the second room may be adjacent or separated from each other.
Also, the orientation of the first room and the second room may be any.
[0128]
The processing of the window function by the window function unit 6 may be performed at any
stage, or may be performed in multiple stages.
That is, the window function unit 6 is between the microphone array and the frequency
conversion unit 1, between the frequency conversion unit 1 and the spatial frequency conversion
unit 2, between the spatial frequency conversion unit 2 and the conversion filter unit 3, and a
conversion filter unit It may be provided between at least one of the space frequency inverse
transform unit 4 and the space frequency inverse transform unit 5.
When processing of the window function is performed on the signal input to each part of each
part of the sound field collection and reproduction device, processing of the window function is
performed in the same manner as described above instead of the input signal. Process the signal
after the
[0129]
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In addition, the window function unit 6 may be omitted.
In this case, in the first embodiment, the speaker Si-j reproduces sound based on the time domain
signal P <d> ij (t) as i = 1,. In the second embodiment, the speaker Si reproduces sound based on
the time domain signal P <d> i (t) as i = 1,.
[0130]
As long as the sound field sound collecting and reproducing apparatus includes the conversion
filter unit 3, it does not have to include other units. For example, the sound field sound collection
and reproduction apparatus may be configured of the conversion filter unit 3, the spatial
frequency inverse conversion unit 4, and the frequency inverse conversion unit 5. Further, the
sound field sound collecting and reproducing apparatus may be configured of the frequency
conversion unit 1, the spatial frequency conversion unit 2, and the conversion filter unit 3.
[0131]
The processing of the frequency conversion unit 1 and the processing of the spatial frequency
conversion unit 2 may be performed simultaneously. Similarly, the process of the spatial
frequency inverse transform unit 4 and the process of the frequency inverse transform unit 5
may be performed simultaneously. Also, the space frequency conversion unit 2 and the space
frequency inverse conversion unit 4 may be interchanged.
[0132]
The sound field sound collecting and reproducing apparatus can be realized by a computer. In
this case, the processing content of each part of this apparatus is described by a program. And
each part in this apparatus is implement | achieved on a computer by running this program by
computer.
[0133]
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The program describing the processing content can be recorded in a computer readable
recording medium. Further, in this embodiment, these devices are configured by executing a
predetermined program on a computer, but at least a part of the processing contents may be
realized as hardware.
[0134]
The present invention is not limited to the above-described embodiment, and various
modifications can be made without departing from the spirit of the present invention.
[0135]
Reference Signs List 1 frequency conversion unit 2 space frequency conversion unit 3 conversion
filter unit 4 space frequency inverse conversion unit 5 frequency inverse conversion unit 6
window function unit
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