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JP2018093379

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DESCRIPTION JP2018093379
The present invention provides a sound field estimation technique capable of estimating the
sound pressure of a collected sound signal collected from a plane wave decomposition
expression of a predetermined sound pressure using a virtually arranged hard-spherical spherical
microphone array. . A position caused by a shift between an origin and a center position RB in a
direction wq indicated by the incident angle (θq, φq) from an incident angle (θq, φq) of a
plane wave q and a center position RB of a rigid sphere type spherical microphone array. A phase
difference shifted decomposition that is a decomposition coefficient reflecting the phase
difference in the direction wq from the phase difference calculation unit 110 that calculates the
phase difference Aq, the phase difference Aq, and the decomposition coefficient aq (ω) of the
plane wave q that constitutes the sound field From the decomposition coefficient phase
difference shift unit 120 for calculating the coefficient a'q (ω) and the phase difference shifted
decomposition coefficient a'q (ω), the three-dimensional position Rj of the j-th microphone on
the rigid sphere type spherical microphone array And a sound pressure calculator 130 that
calculates the sound pressure pB (ω, Rj). [Selected figure] Figure 1
Sound field estimation device, sound field estimation method, program
[0001]
The present invention relates to a sound field estimation technique, and more particularly to a
technique for estimating the sound pressure of a collected sound signal by a hard-spherical
spherical microphone array using a plane wave decomposition representation of sound pressure.
[0002]
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1
In recent years, the number of channels and the number of speakers used for audio reproduction
have been increased from 2 to 5.1 and further to 22.1 in order to enhance the sense of reality or
expand the reproduction area.
It is important to measure and estimate the reproduced sound field for evaluation and
verification of the reproduction method in which the number of channels and the like are
expanded.
[0003]
Non-patent document 1 proposes a method using a spherical microphone array as such a sound
field estimation method. In this method, signals are picked up by a plurality of microphones
arranged in a rigid sphere type spherical microphone array having baffles, plane wave
decomposition of the sound field is determined from the multi-channel signal, and the sound field
is estimated. In addition, Non-Patent Document 2 shows a method of obtaining a sound field in a
wider range by obtaining plane wave decomposition of a sound field using two open-ball type
(open type) spherical microphone arrays without baffles. .
[0004]
A method of plane wave decomposition of the sound field may be used as a method of estimating
the sound field as described above. The plane wave decomposition representation of the sound
field will be described below.
[0005]
[Planar wave decomposition expression of sound field] Plane wave q (q = 1, 2,..., Q) of amplitude
1 incident on the origin of the three-dimensional coordinate system at the incident angle (θ q, φ
q) ) Is considered to be decomposed (Q is an integer of 1 or more, θ q is an elevation angle, and
φ q is an azimuth angle). Further, wq is a direction indicated by the incident angle (θq, φq) of
the plane wave q.
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[0006]
The sound pickup signal in the sound field can be expressed as a linear combination of the sound
pressure of a plane wave. Let ω be the angular frequency, c be the speed of sound, k = ω / c, aq
(ω) (q = 1, 2, ..., Q) be the decomposition coefficients of the plane wave q that makes up the
sound field. The sound pressure p (ω, R) of the sound pickup signal of the sound field at the
three-dimensional position R indicating is expressed by equation (1).
[0007]
[0008]
However, k ^ q is a vector represented by Formula (2).
Here, i is an imaginary unit, and. Is an inner product symbol.
[0009]
[0010]
Equation (1) is expressed as a linear combination of the sound pressure p (ω, R) of the collected
signal at the three-dimensional position R and the sound pressure exp (ik ^ q R) of each plane
wave at the three-dimensional position R It means that.
[0011]
The decomposition coefficients aq (ω) (q = 1, 2,..., Q) of the plane wave q can be determined, for
example, using the method described in Non-Patent Document 2.
[0012]
For example, the sound pressure p (ω, R) of the sound collection signal collected by the virtual
microphone virtually arranged at the three-dimensional position R on the spherical surface of
radius ra (ra> 0) centering on the three-dimensional position RB Is expressed by equation (3).
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[0013]
[0014]
However, the arrangement position R of the virtual microphone is expressed by equation (4)
using a set (Θ, Φ) of elevation angle and azimuth angle of the three-dimensional position R
viewed from the center RB of the spherical surface.
[0015]
[0016]
This corresponds to measuring the sound pressure by the microphones on the spherical surface
of the open sphere type spherical microphone array of the radius ra virtually arranged at the
three-dimensional position RB.
[0017]
Placing the spherical microphone array at the three-dimensional position RB means placing the
spherical microphone array so that the center of the spherical surface of the spherical
microphone array coincides with the three-dimensional position RB.
[0018]
B. Rafaely, "Analysis and Design of Spherical Microphone Arrays", IEEE Trans.
Speech Audio Processing, Vol. 13, No. 1, pp. 135-143, Jan.
2005.
Atsushi Emura, "Sound Field Interpolation Estimation with Two Spherical Microphone Arrays,"
Proceedings of the Acoustical Society of Japan, pp. 589-590, March 2016.
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4
[0019]
By the way, in signal processing using a spherical microphone array, there are many methods
based on a rigid spherical spherical microphone array instead of an open spherical spherical
microphone array.
This is because, in an open-sphere type spherical microphone array, it is necessary to expose
parts such as a skeleton and a cable that support the microphone, and acoustic reflection and
interference between the parts are likely to adversely affect the sound field measurement. It is
because it is not easy to measure the sound field accurately.
On the other hand, a rigid sphere type spherical microphone array can adopt such a
configuration that such components can be accommodated inside the baffle, so that the adverse
effect on the sound field due to the components can be eliminated. It is easy to measure the
sound field accurately.
[0020]
The sound pressure p (ω, R) represented by the equation (3) is measured by a microphone on
the spherical surface of an open sphere type spherical microphone array of a radius ra virtually
arranged at the three-dimensional position RB.
However, since the rigid-sphere type spherical microphone array has a baffle in its structure, the
sound pressure measured by the microphone on the spherical surface of the rigid-sphere type
spherical microphone array of the radius ra virtually arranged at the three-dimensional position
RB is Is different from the sound pressure p (ω, R) represented by
That is, the sound pressure p (ω, R) expressed by the equation (3) can not be used as it is for
signal processing of a collected sound signal collected using a hard-sphere type spherical
microphone array.
[0021]
Therefore, the present invention provides a sound field estimation technique capable of
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estimating the sound pressure of a collected sound signal collected from a plane wave
decomposition representation of a predetermined sound pressure using a virtually arranged
hard-spherical spherical microphone array. The purpose is to
[0022]
One aspect of the present invention is that the sound pressure p (ω, R) of the sound collection
signal of the sound field at the three-dimensional position R indicating the position in the threedimensional coordinate system is incident angle (θq, φq) to the origin of the coordinate system.
Plane wave q (q = 1, 2,..., Q) (where Q is an integer of 1 or more, θ q is an elevation angle, and φ
q is an azimuth angle), and the plane wave of the following equation Shall be expressed in
decomposition expression,
[0023]
[0024]
Where ω is the angular frequency, c is the speed of sound, k = ω / c, aq (ω) (q = 1, 2,..., Q) is the
decomposition coefficient of the plane wave q that constitutes the sound field, k ^ q (q Let = 1, 2,
..., Q) be a vector represented by the following equation, i be an imaginary unit, and.
[0025]
[0026]
J number (J11) of the number of microphones disposed on the spherical surface of the rigid
sphere type spherical microphone array virtually disposed in the sound field, elevation angle and
direction indicating the arrangement position of the microphones in the rigid sphere type
spherical microphone array A set of angles (Θ j, j j) (j = 1, 2,..., J), a radius of the spherical surface
of the hard-sphere type spherical microphone array ra (ra> 0), a center of the spherical surface of
the hard-sphere type spherical microphone array A central position which is a three-dimensional
position shown is RB, and a direction indicated by the incident angle (θq, φq) from the incident
angle (θq, φq) (q = 1, 2,..., Q) and the central position RB. A phase difference calculation unit
that calculates a phase difference Aq (q = 1, 2,..., Q) caused by a shift between the origin and the
center position RB for wq, and the phase difference Aq (q = 1, 2,. Q) and a decomposition
coefficient that reflects a phase difference caused by a shift between the origin and the center
position RB in the direction wq from the decomposition coefficient aq (ω) (q = 1, 2,..., Q)
Difference Shiff A decomposition coefficient phase difference shift unit for calculating a scaled
decomposition coefficient a ′ q (ω) (q = 1, 2,..., Q), and the phase difference shifted
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decomposition coefficient a ′ q (ω) (q = 1, Sound pressure p B (ω, R j) at the three-dimensional
position R j of the j-th microphone (j is an integer of 1 or more and J or less) on the rigid sphere
type spherical microphone array Sound pressure calculation unit that calculates
[0027]
[0028]
including.
[0029]
According to the present invention, it is possible to estimate the sound pressure of a collected
sound signal picked up from a plane wave decomposition expression of a predetermined sound
pressure using a virtually arranged hard sphere type spherical microphone array.
[0030]
FIG. 1 shows an example of the configuration of a sound field estimation apparatus 100.
FIG. 6 shows an example of the operation of the sound field estimation apparatus 100.
[0031]
Hereinafter, embodiments of the present invention will be described in detail.
Note that components having the same function will be assigned the same reference numerals
and redundant description will be omitted.
[0032]
<Notation method> _ (underscore) represents a subscript.
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For example, x <y_z> indicates that yz is a superscript for x, and xy_z indicates that yz is a
subscript for x.
[0033]
First Embodiment First, the sound pressure due to the plane wave q in the case where a hard
sphere type spherical microphone array model and a hard sphere type spherical microphone
array are arranged will be described.
[0034]
[Hard sphere type spherical microphone array model] It is considered to virtually arrange a hard
sphere type spherical microphone array in a sound field and estimate its sound collection signal.
Therefore, in practice, the rigid-spherical spherical microphone array is not arranged in the
sound field.
[0035]
The number of microphones disposed on the spherical surface of a rigid sphere type spherical
microphone array virtually disposed in the sound field is J (J ≧ 1), elevation angle and azimuth
angle indicating the placement position of the microphone in the rigid sphere type spherical
microphone array (Θj, jj) (j = 1, 2, ..., J), the radius of the spherical surface of the hard-sphere
type spherical microphone array ra (ra> 0), a three-dimensional position indicating the center of
the spherical surface of the hard-sphere type spherical microphone array Let RB be the central
position.
Also, let Wj be the direction indicated by the set of elevation angle and azimuth angle (j j, W j).
[0036]
The three-dimensional position Rj of the j-th microphone (j = 1, 2,..., J) on the rigid sphere type
spherical microphone array is the combination of elevation angle and azimuth angle (Θj, jj) from
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the central position RB of the rigid sphere spherical microphone array Since it is a measurement,
it is represented by Formula (5).
[0037]
[0038]
[Sound pressure due to plane wave q in the case where a hard sphere type spherical microphone
array is arranged] A hard sphere type spherical microphone array of radius ra is virtually
arranged at the three dimensional position RB, and the plane wave q of amplitude 1 is the origin
of the three dimensional coordinate system. Let us consider the case where light is incident at an
incident angle (.theta.q, .phi.q) (a plane wave q of amplitude 1 is incident from the direction wq).
[0039]
In this case, the sound pressure pq (ω, RB) due to the incident wave at the center position RB of
the virtually arranged rigid sphere type spherical microphone array is expressed by equation (6).
[0040]
[0041]
However, when a hard sphere type spherical microphone array is actually arranged, the sound
field is composed of the incident wave and the scattered wave.
Therefore, first, the three-dimensional position Rj of the j-th microphone (j is an integer greater
than or equal to 1 and less than J) on the rigid sphere type spherical microphone array when the
rigid sphere type spherical microphone array is virtually arranged at the origin of the three
dimensional coordinate system. Consider the sound pressure pq, O (ω, Rj <'>) due to the plane
wave q at <'>.
3The dimensional position Rj <'> is expressed by the equation (7), and the sound pressure pq, O
(ω, Rj <'>) by the plane wave q is given by the equation (8).
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[0042]
[0043]
[0044]
Here, Pn (x) is a Legendre function of order n, jn (x) is a spherical Bessel function of order n, and
hn (x) is a first kind Hankel function of order n.
Further, jn '(x) and hn' (x) are differential functions of jn (x) and hn (x), respectively, and ΨW_j
and w_q are angles formed by the direction Wj and the direction wq.
Note that k = ω / c.
[0045]
Next, in the case where the hard-sphere spherical microphone array is virtually arranged at the
three-dimensional position RB, the j-th microphone (j is an integer of 1 or more and J or less) on
the three-dimensional position Rj on the hard-sphere spherical microphone array Consider the
sound pressure pq, B (ω, Rj) due to the plane wave q.
The sound pressures pq and B (ω, Rj) due to the plane wave q can be derived from the equations
(6) and (8) in consideration of the phase difference.
Specifically, it is expressed by equation (9).
[0046]
[0047]
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[Sound Field Estimation Device 100] The sound field estimation device 100 will be described
below with reference to FIGS.
As shown in FIG. 1, the sound field estimation apparatus 100 includes a phase difference
calculation unit 110, a decomposition coefficient phase difference shift unit 120, a sound
pressure calculation unit 130, and a recording unit 190.
The recording unit 190 is a component that appropriately records information necessary for the
process of the sound field estimation apparatus 100.
[0048]
3The sound pressure p (ω, R) of the sound pickup signal of the sound field at the threedimensional position R is a plane wave q (q = 1, 2,) that is incident on the origin of the threedimensional coordinate system at an incident angle (θq, φq) It is assumed that it is expressed
by plane wave decomposition expression like a formula (1) using ..., Q).
[0049]
[0050]
Here, ω is an angular frequency, c is the speed of sound, k = ω / c, aq (ω) (q = 1, 2,..., Q) is a
decomposition coefficient of plane wave q constituting a sound field, k ^ q (q = 1, 2,..., Q) are
vectors represented by equation (2).
[0051]
[0052]
The incident angle (θq, φq) (q = 1, 2,..., Q) of the plane wave q to the origin and the
decomposition coefficient aq (ω) (q = 1, 2,. It may be calculated by the plane wave
decomposition method of
[0053]
The sound field estimation apparatus 100 includes an incident angle (θ q, φ q) (q = 1, 2,..., Q) to
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the origin of a plane wave q which is a component of a plane wave decomposition representation
of a sound field and a plane wave q constituting a sound field. The j-th microphone (j is an
integer greater than or equal to 1 and less than J) from the resolution coefficient aq (ω) (q = 1,
2,..., Q) of The sound pressure pB (ω, Rj) at the three-dimensional position Rj of is estimated and
output.
[0054]
The operation of the sound field estimation apparatus 100 will be described according to FIG.
The phase difference calculation unit 110 calculates the phase difference Aq (q = 1, 2,..., Q) from
the incident angle (θq, φq) (q = 1, 2,..., Q) and the center position RB ( S110).
The phase difference Aq is generated due to the deviation of the origin and the center position
RB in the direction wq indicated by the incident angle (θq, φq).
The phase difference Aq (q = 1, 2, ..., Q) is calculated according to equation (10).
[0055]
[0056]
The decomposition coefficient phase difference shift unit 120 generates a phase difference from
the phase difference Aq (q = 1, 2,..., Q) calculated in S110 and the decomposition coefficient aq
(ω) (q = 1, 2,. The shifted decomposition coefficients a ′ q (ω) (q = 1, 2,..., Q) are calculated
(S120).
The phase difference shifted decomposition coefficient a ′ q (ω) is a decomposition coefficient
reflecting the phase difference caused by the deviation of the origin and the center position RB in
the direction wq.
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The phase difference shifted decomposition coefficients a 'q (ω) (q = 1, 2, ..., Q) are calculated
according to equation (11).
[0057]
[0058]
The sound pressure calculation unit 130 uses the j-th microphone (j is 1) on the hard sphere type
spherical microphone array from the phase difference shifted decomposition coefficient a 'q (ω)
(q = 1, 2, ..., Q) calculated in S120. The sound pressure pB (ω, Rj) at the three-dimensional
position Rj of the above J) is calculated (S130).
Specifically, it is calculated according to equation (12) using the phase difference shifted
decomposition coefficient a 'q (ω).
That is, the sound pressure in the direction wq calculated using the phase difference shifted
decomposition coefficient a 'q (ω) is added.
[0059]
[0060]
Since the sound pressure pB (ω, Rj) in the equation (12) is defined with the limit (infinite sum of
n), actually, n is a finite n (hereinafter, N is an integer of 0 or more) It is necessary to calculate
the sound pressure pB (ω, Rj) by performing numerical calculation using
That is, as a formula for calculating the sound pressure pB (ω, Rj), formula (13) is used instead of
formula (12).
[0061]
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[0062]
For example, when ra = 4 cm, it may be about N = 10.
Even at N = 10, it is possible to estimate the sound pressure with sufficient accuracy.
[0063]
According to the invention of this embodiment, it is possible to estimate the sound pressure of
the collected sound signal picked up using a virtually arranged hard-spherical spherical
microphone array from a plane wave decomposition expression of a predetermined sound
pressure .
For example, a plane wave decomposition representation of sound pressure is obtained from a
collected sound signal of a rigid sphere type spherical microphone array actually arranged, and a
rigid sphere type spherical microphone array is virtually arranged at another position from this
plane wave decomposition representation. It becomes possible to estimate the collected signal.
Also, for example, the sound pressure of the collected sound signal is estimated using a virtually
arranged hard sphere type spherical microphone array from a plane wave decomposition
expression of sound pressure determined using an open sphere type spherical microphone array.
Is possible.
Thus, the sound pressure represented by a predetermined plane wave decomposition expression
obtained without using a hard-sphere type spherical microphone array is used for signal
processing assuming as an input a collected sound signal collected using the hard-sphere type
spherical microphone array You will be able to
[0064]
<Modification> The present invention is not limited to the above-described embodiment, and it
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goes without saying that changes can be made as appropriate without departing from the spirit
of the present invention.
The various processes described in the above embodiment are not only executed chronologically
according to the order described, but may be executed in parallel or individually depending on
the processing capability of the apparatus executing the process or the necessity.
[0065]
<Supplement> The device of the present invention is, for example, an input unit to which a
keyboard can be connected, an output unit to which a liquid crystal display etc can be connected
as a single hardware entity, and a communication device capable of communicating outside the
hardware entity Communication unit to which the communication cable can be connected, CPU
(Central Processing Unit, may be provided with a cache memory, a register, etc.), RAM or ROM
which is a memory, external storage device which is a hard disk, and input / output units thereof
, A communication unit, a CPU, a RAM, a ROM, and a bus connected so as to enable exchange of
data between external storage devices.
If necessary, the hardware entity may be provided with a device (drive) capable of reading and
writing a recording medium such as a CD-ROM.
Examples of physical entities provided with such hardware resources include general purpose
computers.
[0066]
The external storage device of the hardware entity stores a program necessary for realizing the
above-mentioned function, data required for processing the program, and the like (not limited to
the external storage device, for example, the program is read) It may be stored in the ROM which
is a dedicated storage device).
In addition, data and the like obtained by the processing of these programs are appropriately
stored in a RAM, an external storage device, and the like.
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[0067]
In the hardware entity, each program stored in the external storage device (or ROM etc.) and data
necessary for processing of each program are read into the memory as necessary, and
interpreted and processed appropriately by the CPU .
As a result, the CPU realizes predetermined functions (each component requirement expressed as
the above-mentioned,...
[0068]
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. Further,
the processes described in the above embodiment may be performed not only in chronological
order according to the order of description but also may be performed in parallel or individually
depending on the processing capability of the apparatus executing the process or the necessity. .
[0069]
As described above, when the processing function in the hardware entity (the apparatus of the
present invention) described in the above embodiment is implemented by a computer, the
processing content of the function that the hardware entity should have is described by a
program. Then, by executing this program on a computer, the processing function of the
hardware entity is realized on the computer.
[0070]
The program describing the processing content can be recorded in a computer readable
recording medium. As the computer readable recording medium, any medium such as a magnetic
recording device, an optical disc, a magneto-optical recording medium, a semiconductor memory,
etc. may be used. Specifically, for example, as a magnetic recording device, a hard disk device, a
03-05-2019
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flexible disk, a magnetic tape or the like as an optical disk, a DVD (Digital Versatile Disc), a DVDRAM (Random Access Memory), a CD-ROM (Compact Disc Read Only) Memory), CD-R
(Recordable) / RW (Rewritable), etc. as magneto-optical recording medium, MO (Magneto-Optical
disc) etc., as semiconductor memory EEP-ROM (Electronically Erasable and Programmable Only
Read Memory) etc. Can be used.
[0071]
Further, this program is distributed, for example, by selling, transferring, lending, etc. a portable
recording medium such as a DVD, a CD-ROM or the like in which the program is recorded.
Furthermore, this program may be stored in a storage device of a server computer, and the
program may be distributed by transferring the program from the server computer to another
computer via a network.
[0072]
For example, a computer that executes such a program first temporarily stores a program
recorded on a portable recording medium or a program transferred from a server computer in its
own storage device. Then, at the time of execution of the process, the computer reads the
program stored in its own recording medium and executes the process according to the read
program. Further, as another execution form of this program, the computer may read the
program directly from the portable recording medium and execute processing according to the
program, and further, the program is transferred from the server computer to this computer
Each time, processing according to the received program may be executed sequentially. In
addition, a configuration in which the above-described processing is executed by a so-called ASP
(Application Service Provider) type service that realizes processing functions only by executing
instructions and acquiring results from the server computer without transferring the program to
the computer It may be Note that the program in the present embodiment includes information
provided for processing by a computer that conforms to the program (such as data that is not a
direct command to the computer but has a property that defines the processing of the computer).
[0073]
Further, in this embodiment, the hardware entity is configured by executing a predetermined
program on a computer, but at least a part of the processing content may be realized as
hardware.
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