close

Вход

Забыли?

вход по аккаунту

?

JP2014150416

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2014150416
Abstract: The present invention provides a sound field collection and reproduction technique
capable of reproducing a sound field with higher accuracy than in the prior art when using a
circular microphone array / speaker array. SOLUTION: At least two microphones are arranged on
a circumference of a radius R of a first space centering on an axis of a cylindrical rigid baffle of
radius R and circumferential direction of the baffle circumferential direction, Assuming that at
least two speakers are disposed on the circumference of a virtual cylinder of radius R of a second
space different from the first space, the circle in which the speakers are disposed is a secondary
sound source circle, and R is a secondary sound source Defined as a distance from the center of a
circle to a point on the circumference where amplitudes are matched, for a space-time frequency
domain signal P ~ (ω) generated based on a signal collected by a microphone Filter F (ω) is
generated to generate a filtered signal D ~ (ω). [Selected figure] Figure 1
Sound field sound collecting and reproducing apparatus, method and program
[0001]
This invention is a technology of Wave Field Synthesis, Ambisonics, which picks up a sound
signal with a microphone installed in a certain sound field and reproduces the sound field with a
speaker using the sound signal. About.
[0002]
Wavefront synthesis and ambisonics are techniques for virtually reproducing the sound field of a
remote place using a plurality of microphones and speakers.
03-05-2019
1
As such technology, for example, the technology described in Non-Patent Document 1 is known.
Since applications such as remote communication systems require real-time sound collection and
reproduction, the sound pressure collected by a general microphone array is unique to a sound
field reproduction signal for output by a general speaker array. Need to be convertible to
[0003]
Oyama, Furuya, Kazukazu Kazukazu, Haneda, Suzuki, “Wavefront Reconstruction Filter for
Cylindrical Microphone-Speaker Array”, September 2012, Proceedings of the Fall Meeting of
the Acoustical Society of Japan, pp. 605-608
[0004]
In the technique described in Non-Patent Document 1, assuming that a cylindrical microphone
array / speaker array is used, a filter for conversion has been derived.
Therefore, if this filter is applied to a circular microphone array / speaker array, the sound field
can not be reproduced with high accuracy, and the sound field can be reproduced with high
accuracy such that sound comes from all directions around the listener. There was a possibility
that could not.
[0005]
It is an object of the present invention to reproduce a sound field with higher accuracy than in
the prior art when using a circular microphone array / speaker array, and to increase the sound
field such that sound comes from all directions around the listener. Abstract: A sound field sound
collecting and reproducing apparatus, method, and program that can be reproduced with
accuracy.
[0006]
In order to solve the above-mentioned subject, sound field sound collection playback device by
one mode of this invention is the 1st space which makes the circumferential direction of the
baffle circumferential direction centering on the axis of baffle of cylindrical rigid body of radius
Rb. Assuming that at least two microphones are arranged around the radius Rm of R, Rm R Rb,
the circumferential direction of the baffle is φ direction, j is an imaginary unit, ω is a frequency,
03-05-2019
2
c is a speed of sound, k = ω / c, m is the order in the φ direction, H <(1)> m (·) is the first kind
Hankel function of the m order, Jm (·) is the Bessel function of the m order, H <( 1) Let> m '(.) Be
the derivative of the first-class Hankel function H <(1)> m (.) Of the m-th, Jm' (.) Be the derivative
of the Bessel function Jm (.) Of the m-th, Let wm be a weight determined on the basis of m, A (ω)
be a complex number determined on the basis of ω, and at least two speakers be disposed on the
circumference of a virtual cylinder having a radius Rs of a second space different from the first
space Have been The circle on which the signal is placed is the secondary sound source circle,
and Rref is the distance from the center of the secondary sound source circle to the point on the
circumference where the amplitudes are matched, generated based on the signal collected by the
microphone A conversion filter unit that generates a filtered signal D ~ m (ω) by applying a filter
F ~ m (ω) defined by the following equation to the space-time frequency domain signal P ~ m (ω);
[0007]
[0008]
A space-frequency inverse transform unit that transforms the filtered signal D to m (ω) into a
frequency domain signal by inverse Fourier transform of space, and a time domain signal that is
transformed into a time domain signal by inverse Fourier transform And a frequency inverse
converter for outputting the area signal to the speaker.
[0009]
According to another aspect of the present invention, there is provided an acoustic field sound
collecting and reproducing apparatus comprising: a cylinder-shaped rigid baffle having a radius
Rb and a radius of Rm in a first space whose circumferential direction is a circumferential
direction of the baffle; Assuming that at least two microphones are arranged, Rm ≧ Rb, the
circumferential direction of the baffle is φ direction, j is an imaginary unit, ω is a frequency, c is
a speed of sound, k = ω / c, m Is an order in the φ direction, H <(1)> m (·) is a first kind Hankel
function of the m order, Jm (·) is a Bessel function of the m order, H <(1)> m ′ (· Let m) be the
derivative of the Hank function H <(1)> m (.) Of the m-th, Jm '(.) Be the derivative of the Bessel
function Jm (.) Of the m-th, and wm be determined based on m Assuming that A (ω) is a complex
number determined based on ω, and at least two speakers are disposed on the circumference of
a virtual cylinder having a radius Rs of a second space different from the first space Two placed
circles A frequency converter configured to convert a signal collected by the microphone into a
frequency domain signal by Fourier transform, where R so is the distance from the center of the
secondary sound source circle to the point on the circumference where the amplitude is matched.
A spatial frequency conversion unit that converts a frequency domain signal to a space-time
frequency domain signal P ~ m (ω) by the Fourier transform of A conversion filter unit that
03-05-2019
3
generates filtered signal D ~ m (ω) by applying F ~ m (ω);
[0010]
[0011]
including.
[0012]
According to another aspect of the present invention, there is provided a sound field collection
and reproduction apparatus, in which at least two microphones are arranged around a circle of
radius Rm of a first space centered on the center of a spherical rigid baffle of radius Rb. It is
assumed that Rm 円 Rb, the circle in which the microphone is disposed is the receiving circle, the
circumferential direction of the receiving circle is the φ direction, and the circumference of the
large circle of the plane perpendicular to the receiving circle and the baffle Let the direction be
the θ direction, j be the imaginary unit, ω be the frequency, c be the speed of sound, k = ω / c,
m be the order in the φ direction, n be the order in the θ direction, H <(1) > Let m (·) be the first
kind Hankel function of order m, Jm (·) be the Bessel function of order m, h <(1)> n (·) be the first
kind of sphere Hankel function of order n, Let jn (·) be the n-th-order spherical Bessel function, h
<(1)> n '(.) be the derivative of the n-th-order first-class sphere Hankel function h <(1)> n (·), jn'
Let (·) be the derivative of the n-th-order spherical Bessel function jn (·), and P <m> n (·) be a
regende Let 陪 be a function, w m be a weight determined based on m, A (ω) be a complex
number determined based on ω, and at least two speakers be virtual spheres of a second space
radius Rs different from the first space It is assumed that the circle is arranged on the
circumference of the great circle, the circle on which the speaker is arranged is the secondary
sound source circle, and Rref is the distance from the center of the secondary sound source circle
to the point on the circumference where the amplitudes are matched. A filter F ~m (ω) defined by
the following equation is applied to a space-time frequency domain signal P ~m (ω) generated
based on a collected signal, and a post-filtering signal D ~m ( a conversion filter unit that
generates ω),
[0013]
[0014]
A space-frequency inverse transform unit that transforms the filtered signal D to m (ω) into a
frequency domain signal by inverse Fourier transform of space, and a time domain signal that is
transformed into a time domain signal by inverse Fourier transform And a frequency inverse
03-05-2019
4
converter for outputting the area signal to the speaker.
[0015]
According to another aspect of the present invention, there is provided a sound field collection
and reproduction apparatus, in which at least two microphones are arranged around a circle of
radius Rm of a first space centered on the center of a spherical rigid baffle of radius Rb. It is
assumed that Rm 円 Rb, the circle in which the microphone is disposed is the receiving circle, the
circumferential direction of the receiving circle is the φ direction, and the circumference of the
large circle of the plane perpendicular to the receiving circle and the baffle Let the direction be
the θ direction, j be the imaginary unit, ω be the frequency, c be the speed of sound, k = ω / c,
m be the order in the φ direction, n be the order in the θ direction, H <(1) > Let m (·) be the first
kind Hankel function of order m, Jm (·) be the Bessel function of order m, h <(1)> n (·) be the first
kind of sphere Hankel function of order n, Let jn (·) be the n-th-order spherical Bessel function, h
<(1)> n '(.) be the derivative of the n-th-order first-class sphere Hankel function h <(1)> n (·), jn'
Let (·) be the derivative of the n-th-order spherical Bessel function jn (·), and P <m> n (·) be a
regende Let 陪 be a function, w m be a weight determined based on m, A (ω) be a complex
number determined based on ω, and at least two speakers be virtual spheres of a second space
radius Rs different from the first space It is assumed that the circle is arranged on the
circumference of the great circle, the circle on which the speaker is arranged is the secondary
sound source circle, and Rref is the distance from the center of the secondary sound source circle
to the point on the circumference where the amplitudes are matched. A frequency conversion
unit that converts the collected signal into a frequency domain signal by Fourier transform; a
spatial frequency conversion unit that converts the frequency domain signal into a space-time
frequency domain signal P to m (ω) by Fourier transform of space; A conversion filter unit that
generates a filtered signal D ~ m (ω) by applying a filter F ~ m (ω) defined by the following
equation to the space-time frequency domain signal P ~ m (ω);
[0016]
[0017]
including.
[0018]
The filter for the circular microphone array and the speaker array can be used to convert the
sound pickup signal of the circular microphone array into a drive signal of the circular speaker
array to reproduce the sound field. It becomes possible to reproduce with high precision a sound
field in which sound comes from all directions.
03-05-2019
5
[0019]
The figure for demonstrating the example of arrangement | positioning of a microphone and a
speaker.
FIG. 2 is a functional block diagram showing an example of a sound field sound collecting and
reproducing apparatus.
The flowchart which shows the example of the sound field sound collection reproduction method.
The figure for demonstrating the example of arrangement | positioning of a microphone and a
speaker.
[0020]
First Embodiment Hereinafter, an embodiment of the present invention will be described with
reference to the drawings.
In the following description, the symbols "~", "<->", etc. used in the text should originally be
written directly above the previous character, but due to the limitations of the text notation
Described in.
In the formula, these symbols are described at their original positions.
Moreover, the processing performed in each element unit of a vector or a matrix is applied to all
elements of the vector or the matrix unless otherwise noted.
[0021]
03-05-2019
6
<Regarding Arrangement of Microphone Array and Speaker Array> As shown in FIG. 1, in the
sound field collection and reproduction apparatus and method of the first embodiment, the axis
of the cylindrical rigid body baffle of the radius Rb of the first space is centered. And a
microphone array composed of Nch microphones M1, M2,..., MNch arranged on the
circumference of a circle of radius Rm whose circumferential direction is the circumferential
direction of the baffle, and the radius Rs of the second space A speaker array formed of Nch
speakers S1, S2,..., SNch arranged on the circumference of a virtual cylinder of The sound field of
the space of is reproduced in the second space.
The circumference of the imaginary cylinder means the circumference of a circle which is a
common part of a plane perpendicular to the axis of the imaginary cylinder and the imaginary
cylinder.
The first space and the second space are mutually different spaces.
In FIG. 1, the sound source S reproduced in the second space is expressed as a sound source S '.
The circle formed by the microphone array is also referred to as a reception circle, and the circle
formed by the speaker array is also referred to as a secondary sound source circle.
In other words, a circle in which the microphone array is arranged is called a receiving circle, and
a circle in which the speaker array is arranged is called a secondary sound source circle.
The axial direction of the baffle is the z direction, and the circumferential direction of the baffle
of radius Rb is the φ direction.
In other words, the φ direction is the circumferential direction of the receiving circle.
The number of microphones disposed in the first space and the number of speakers disposed in
the second space may be different. When the number of microphones is larger than the number
of speakers disposed in the second space, the reproduction signal may be thinned. On the other
03-05-2019
7
hand, when the number of microphones is smaller than the number of speakers arranged in the
second space, the reproduction signal may be interpolated by averaging the channels. As a
method of performing interpolation, for example, linear interpolation or sinc interpolation can be
applied.
[0022]
The microphone array uses two or more microphones to form a circle. For example, as shown in
FIG. 1, Nch microphones are equally spaced on the circumference of a circle of radius Rm whose
center is the axis of the cylindrical rigid body baffle and whose circumferential direction is the
circumferential direction of the baffle. . Nch is a predetermined integer of 2 or more.
[0023]
The radius Rb of the cylindrical rigid body baffle and the distance Rm between the axis of the
baffle and the microphone may be any value as long as Rm ≧ Rb. In the case of Rm = Rb, the
microphone will be disposed on the surface of the circumferential surface of the cylindrical baffle
of radius Rb (= Rm). In the case of Rm> Rb, as shown in FIG. 1, the microphone is disposed at a
position Rm away from the axis of the cylindrical baffle of radius Rb. In other words, the
microphone is placed at a position (Rm-Rb) away from the surface of the peripheral surface of
the baffle. For example, the microphone is disposed by being supported by a thin rod-like
member that protrudes vertically from the circumferential surface of the baffle.
[0024]
Note that the filters F to m (ω) used in the conversion filter unit 4 are derived on the assumption
that the cylinder of the baffle has an infinite length (for details, see <Regarding Derivation of
Filter>). Therefore, (1) the cylinder of the baffle is preferably long, and (2) the installation
position of the microphone is preferably the center of the cylinder length of the baffle. In the
present embodiment, the length of the baffle and the installation position of the microphone are
not limited to (1) and (2), but in the case of (1) and (2), the wavefront closest to the sound
collecting field is synthesized. can do.
[0025]
03-05-2019
8
The Nch microphones arranged on the circumference of a circle of radius Rm are located at
intervals of φcradian, with φc being a predetermined angle. The microphones do not have to be
strictly arranged at equal intervals as long as they are arranged at approximately equal intervals.
That is, it is not necessary that the values of φc, which are the distances to the adjacent
microphones, be strictly the same value, but may be approximately the same value. Also, the
microphones may be arranged at any intervals. That is, the distance between adjacent
microphones φc can take an arbitrary value. However, the sound field can be reproduced with
high accuracy by arranging the microphones at substantially equal intervals, that is, by setting
φc, which is the distance between adjacent microphones, to substantially the same value.
[0026]
The speakers are also arranged in the same manner as the microphones. That is, the speaker
array uses two or more speakers to form a circle. For example, as shown in FIG. 1, Nch speakers
are equally spaced around the circumference of the virtual cylinder. Nch is a predetermined
integer of 2 or more.
[0027]
The Nch speakers arranged on the circumference of the virtual cylinder are located at intervals of
φcradian, where φc is a predetermined angle. The speakers do not have to be strictly arranged
at equal intervals as long as they are arranged at approximately equal intervals. That is, it is not
necessary that the values of φc, which are the distances to the adjacent speakers, be exactly the
same value, and it may be approximately the same value. Also, the speakers may be arranged at
any intervals. That is, an interval φc between adjacent speakers can take an arbitrary value.
However, the sound field can be reproduced with high accuracy by arranging the speakers at
substantially equal intervals, that is, by setting φc, which is an interval between adjacent
speakers, to substantially the same value.
[0028]
The positional relationship of the Nch microphones on the circumference of the receiving circle
is preferably the same as the position of the corresponding Nch speakers of the secondary sound
03-05-2019
9
source circle, but may be different. If the positions are the same, the sound field can be
reproduced more faithfully.
[0029]
The radius Rm of the receiving circle is, for example, about 0.2 m. The radius Rs of the secondary
sound source circle is, for example, about 1.5 m. Although it is assumed in the present
embodiment that RsRRm, the same processing can be applied even if this is not satisfied (that is,
also in the case of Rs <Rm). However, when Rs ≧ Rm, the accuracy of sound field reproduction is
improved. The larger the value of the radius Rm of the circle formed by the microphone array
and the radius Rs of the virtual cylinder, the larger the area can be reproduced, but more
microphones and speakers are required. It is desirable that the radius Rm of the circle formed by
the microphone array and the radius Rs of the virtual cylinder be set experimentally in
consideration of the frequencies of the signals to be collected and reproduced, respectively. Also,
the microphones are arranged outside the sound receiving circle, and the speakers are arranged
inside the secondary sound source circle. The sound collection range targeted by the microphone
array is outside the sound receiving circle, and the reproduction range targeted by the speaker
array is inside the secondary sound source circle.
[0030]
The speaker may be disposed in the air of the second space in an acoustically transparent state,
or may be disposed in the second space in an acoustically non-transparent state. The acoustically
transparent state is a state in which the same transfer characteristic as the transfer characteristic
of the second space in which the speaker is not disposed is maintained. For example, if it is
desired to place the speaker in the air of the second space in an acoustically transparent state,
the speaker may be placed in the air of the second space by being suspended by a thread or fixed
by a thin rod. Be done.
[0031]
The position of the microphone Mi (i = 1, 2,..., Nch) in the first space is expressed as r <−> m, i =
(Rm, φm, i, 0) in a cylindrical coordinate system. The position of the speaker Si (i = 1, 2,..., Nch)
in the second space is expressed as r <−> s, i = (Rs, φs, i, 0) in a cylindrical coordinate system.
03-05-2019
10
[0032]
<Sound Field Sound Collection Reproduction Device> As shown in FIG. 2, the sound field sound
collection reproduction device according to the first embodiment includes a frequency
conversion unit 1, a space frequency conversion unit 3, a conversion filter unit 4, a space
frequency inverse conversion unit 5, and For example, the frequency inverse transform unit 6 is
included to perform the processing of each step illustrated in FIG. 3.
[0033]
The microphones M1, M2,..., And MNch arranged in the first space pick up the sound emitted by
the sound source S in the first space to generate a time domain signal.
The generated signal is sent to the frequency converter 1. A signal at time t collected in the
microphone Mi located at r <−> m, i = (Rm, φm, i, 0) is denoted as pi (t).
[0034]
<Frequency Converter 1> The frequency converter 1 converts the signal pi (t) collected by the
microphone Mi 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 3. ω is a
frequency. A value k = ω / c obtained by dividing ω by the speed of sound c is defined as a wave
number. The wave number is the so-called spatial frequency or angular spectrum. 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 Pi (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 as, for example, equation (1). J in the argument of the function
exp is an imaginary unit.
[0035]
[0036]
03-05-2019
11
<Spatial Frequency Transform Unit 3> The spatial frequency transform unit 3 transforms the
frequency domain signal Pi (ω) into the space-time frequency domain signal P ~m (ω) by Fourier
transform of space (step S3).
The space-time frequency domain signal P ~m (ω) is calculated for each frequency ω. The
converted space-time frequency domain signal P ~m (ω) is sent to the conversion filter unit 4.
The spatial frequency transform unit 3 calculates, for example, P ~m (ω) defined by the equation
(2).
[0037]
[0038]
m is an order in the φ direction.
Here, −M ≦ m ≦ M, and m is an integer. Equation (2) is an example of conversion to the spacetime frequency domain, and Fourier transform of space may be performed by another method.
Also, a method may be used in which equations (1) and (2) are combined to perform a twodimensional DFT.
[0039]
<Transformation Filter Unit 4> The conversion filter unit 4 applies a predetermined filter F to m
(ω) to the space-time frequency domain signal P to m (ω) according to the following equation to
apply filtered signals D to m ω) is generated (step S4). The post-filtering signal D ~m (ω) is sent
to the spatial frequency inverse transform unit 5.
[0040]
[0041]
03-05-2019
12
Rref is the distance from the center of the secondary sound source circle to a point on the
circumference (which is coplanar with the secondary sound source circle) that matches the
amplitude.
Therefore, when Rref = 0, the amplitudes coincide at the center of the secondary sound source
circle, and when Rref ≠ 0, the amplitudes coincide on the concentric circle of the secondary
sound source circle of the radius Rref. In addition, in the case of Rref = 0, a set of points whose
amplitudes coincide with each other from the center of the secondary sound source circle does
not form a circle but becomes a point (the center of the secondary sound source circle). It shall
be included in the expression "circle around which the amplitude is matched from the center of".
In addition, Rref may be rephrased as a distance from the center of the secondary sound source
circle to a point on the same plane as the secondary sound source circle whose amplitude is
matched. In the case of Equation (4), the target sound field coincides with the target sound field
on the circumference of the concentric circle of the secondary sound source circle whose
amplitude is determined by Rref, while in the case of Equation (5) The amplitudes match in). A
(ω) is a complex number (an arbitrary complex number depending on ω) determined based on
ω, and is a value for performing an equalizing operation such as lowering the high frequency
gain, for example. In the case of the equation (5), specifically, the amplitude is the same height as
the speaker array, and is located at the center of the secondary sound source circle or at the
circumferential position of the concentric circle of the secondary sound source circle of radius
Rref. Match wm is a weighting function, and is defined, for example, as follows.
[0042]
[0043]
[0044]
Γ (z) and Yv (z) represent the gamma function and the Neumann function, respectively.
The conversion filter is obtained by numerically calculating the above equation.
03-05-2019
13
The integral value or the like of equation (4) may be approximately calculated, for example,
discretized as in the following equation.
[0045]
[0046]
Here, i is the index of discretization, Δkz is the discretization interval, and I is the range of the
sum.
Expression (11) is an example of a method of discretizing and approximately obtaining an
integral value, and may be discretized by another method. It can be discretized using various
approximation formulas used in the definition of the piecewise quadrature method.
[0047]
Further, when Rb = Rm, that is, when the microphone is disposed on the surface of the peripheral
surface of the cylindrical baffle of radius Rb (= Rm), the equations (4) and (5) are respectively as
follows: It can be simplified.
[0048]
[0049]
It is reproduced in the second space by applying the filter F to m (ω) defined by the equation (4)
or the equation (5), or the equation (4-2) or the equation (5-2) Since the amplitudes of the signals
can be matched on a predetermined circumference, the amplitudes of the reproduced signals are
matched in a wider range than in the past.
[0050]
<Spatial Frequency Inverse Transform Unit 5> The spatial frequency inverse transform unit 5
converts the filtered signal D ~m (ω) into a frequency domain signal Di (ω) by inverse Fourier
transform of space (step S5).
03-05-2019
14
The converted frequency domain signal Di (ω) is sent to the frequency inverse transform unit 6.
The spatial frequency inverse transform unit 5 calculates, for example, the frequency domain
signal Di (ω) defined by equation (12).
[0051]
[0052]
<Frequency Inverse Transform Unit 6> The frequency inverse transform unit 6 converts the
frequency domain signal Di (ω) into a time domain signal di (t) by inverse Fourier transform
(step S6).
The time domain signal di (t) obtained for each frame by the inverse Fourier transform is
appropriately shifted and a linear sum is taken 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 di (t) is sent to the speakers S1, S2, ...,
SNch.
[0053]
The speaker Si reproduces sound based on the time domain signal di (t). For example, as i = 1,...,
Nch, the speaker Si located at r <−> s, i = (Rs, φs, i, 0) reproduces a sound based on the time
domain signal di (t). Thereby, the sound field of the first space can be reproduced in the second
space.
[0054]
03-05-2019
15
As mentioned above, if the number of microphones is greater than the number of speakers, the
time domain signal di (t) may be decimated. On the other hand, when the number of microphones
is smaller than the number of speakers, interpolation may be performed by averaging the time
domain signal di (t). As a method of performing interpolation, for example, linear interpolation or
sinc interpolation can be applied.
[0055]
<Effects> Since it is possible to convert the sound pickup signal of a circular microphone array
into a drive signal of a circular speaker array by using a filter for a circular microphone array /
speaker array and reproduce the sound field, It becomes possible to reproduce with high
precision a sound field in which sound comes from all directions around the listener. Therefore,
the sound field can be reproduced with higher accuracy than in the prior art.
[0056]
<Regarding Derivation of Filter> Hereinafter, the reason why the filters F to m (ω) are
represented as Expression (4) and Expression (5) will be described.
[0057]
Here, the cylindrical coordinate system r <-> = (r, φ, z) is considered.
The sound field on the xy plane is reproduced using the secondary sound source circle arranged
in the reproduction area from the sound pressure distribution acquired by the sound receiving
circle arranged in the sound collection area.
[0058]
A synthetic sound field Psyn (r <->, ω) by secondary sound sources continuously arranged on the
circumference is a secondary sound source drive signal D (r <-> s, ω), a secondary sound source
and a target sound. Using the transfer function G (r <->-r <-> s, ω) between the field, it can be
expressed as follows.
[0059]
03-05-2019
16
[0060]
Since this can be regarded as a convolution with respect to φ of D (·) and G (·), it can be
expressed in the form of a product in the circular harmonic spectrum region as follows.
[0061]
[0062]
On the other hand, the sound pressure distribution Prcv (Rm, 0, φ, ω) obtained on the
circumference of the radius Rm of the sound collection field Prcv (r <->, ω) of the target sound
field Pdes (r <->, ω) It is necessary to express using.
Assuming that an infinite-length rigid cylinder of radius Rb (≦ Rm) is installed centered on the
same position as the receiving circle, the sound collection field Prcv (r <−>, ω) is the incident
sound as in the following equation It can be expressed by the sum of the field Pinc (r <->, ω) and
the scattered sound field Psct (r <->, ω).
Prcv (r <->, ω) = Pinc (r <->, ω) + Psct (r <->, ω) (15) Further, from the boundary condition on
the rigid cylinder,
[0063]
[0064]
Is true.
Also, Pinc (r <->, ω) and Psct (r <->, ω) can be written as follows in the helical wave spectral
region.
03-05-2019
17
[0065]
[0066]
したがって、
[0067]
[0068]
となる。
From the above, assuming that the sound collection field is invariable in the z-axis direction, the
relational expression between the incident sound field and the sound collection field can be
derived as follows.
[0069]
[0070]
Because the target sound field is equal to the incident sound field,
[0071]
[0072]
となる。
Since it is sufficient if the synthetic sound field Psyn (r <->, ω) and the target sound field Pdes (r
<->, ω) coincide with each other,
03-05-2019
18
[0073]
[0074]
Here, for simplicity, it is assumed that G (r <->-r <-> s, ω) is a monopole characteristic.
[0075]
[0076]
Although the conversion equation of the secondary sound source drive signal has been obtained
from the sound pressure distribution on the sound receiving circle above, it is necessary to give
in advance a circle whose amplitude matches the target sound field as r = Rref.
[0077]
Assuming that the secondary sound source is a line sound source, the conversion equation can be
further simplified.
[0078]
[0079]
であることより、
[0080]
[0081]
となる。
However, an actual speaker is close to monopole characteristics, and a correction for linear
sound source approximation is required.
03-05-2019
19
[0082]
[0083]
Because of this, the following frequency characteristics are corrected for each output signal.
[0084]
[0085]
The case of Rb = Rm can be simplified using the following relational expression.
[0086]
[0087]
Second Embodiment A description will be made focusing on parts different from the first
embodiment.
[0088]
<Regarding Arrangement of Microphone Array and Speaker Array> As shown in FIG. 4, in the
sound field collecting and reproducing apparatus and method according to the second
embodiment, a first space centering on the center of the spherical rigid baffle of radius Rb is
used. A microphone array composed of Nch microphones M1, M2, ..., MNch arranged on the
circumference of a circle of radius Rm, and arranged on the circumference of a great circle of a
virtual sphere of radius Rs of the second space The sound field of the first space formed by the
sound generated by the sound source S of the first space using the Nch speakers S1, S2,.
Reproduce in the space of.
The circle formed by the microphone array is also called a receiving circle, and the great circle of
the virtual sphere formed by the speaker array is also called a secondary sound source circle.
A direction perpendicular to the receiving circle and the secondary sound source circle is the z
direction, a circumferential direction of the receiving circle and the secondary sound source
03-05-2019
20
circle is the φ direction, and a large circle of a plane perpendicular to the receiving circle and the
baffle The circumferential direction of the great circle of the plane perpendicular to the
secondary sound source circle and the virtual sphere is taken as the θ direction.
[0089]
In the first embodiment, the microphone and the speaker are respectively arranged on a circle of
radius Rm and a virtual cylinder of radius Rs whose center is the axis of the cylindrical rigid
baffle of radius Rb and whose circumferential direction is the circumferential direction of the
baffle. It is arranged.
On the other hand, in the second embodiment, the microphone and the speaker are respectively
disposed around the circle of the radius Rm of the first space and the circle of the imaginary
sphere of the radius Rs centered on the center of the spherical rigid baffle of the radius Rb. It is
done.
[0090]
The position of the microphone Mi (i = 1, 2,..., Nch) in the first space is expressed as r <−> m, i =
(Rm, π / 2, φm, i) in a spherical coordinate system.
The position of the speaker Si (i = 1, 2,..., Nch) in the second space is expressed as r <−> s, i =
(Rs, π / 2, φs, i) in a spherical coordinate system.
[0091]
<Transformation Filter Unit 4> The conversion filter unit 4 applies a predetermined filter F to m
(ω) to the space-time frequency domain signal P to m (ω) according to the following equation to
apply filtered signals D to m ω) is generated (step S4).
The post-filtering signal D ~m (ω) is sent to the spatial frequency inverse transform unit 5.
03-05-2019
21
[0092]
[0093]
Rref is the distance from the center of the secondary sound source circle to a point on the
circumference (which is coplanar with the secondary sound source circle) that matches the
amplitude.
n is an order in the θ direction.
h <(1)> n (.), jn (.), h <(1)> n '(.), jn' (.), P <m> n (.) are each n-th first Seed sphere Hankel function,
nth sphere Bessel function, nth first class sphere Hankel function h <(1)> differentiation of n (·),
nth sphere Bessel function jn (•) differentiation, Legendre function And is defined as follows.
[0094]
[0095]
Pn (·) represents a Legendre polynomial.
The conversion filter is obtained by numerically calculating the above equation.
[0096]
Further, when Rb = Rm, that is, when the microphone is disposed on the surface of the peripheral
surface of the cylindrical baffle of radius Rb (= Rm), the equations (31) and (32) are respectively
as follows: It can be simplified.
[0097]
03-05-2019
22
[0098]
Reproduced in the second space by applying the filter F to m (ω) defined by the equation (31) or
the equation (32), or the equation (31-2) or the equation (32-2) Since the amplitudes of the
signals can be matched on a predetermined circumference, the amplitudes of the reproduced
signals are matched in a wider range than in the past.
[0099]
With such a configuration, the same effect as that of the first embodiment can be obtained.
[0100]
<Regarding Derivation of Filter> Hereinafter, the reason why the filters F to m (ω) are
represented as Expression (31) and Expression (32) will be described.
[0101]
Here, the spherical coordinate system r <-> = (r, θ, φ) is considered.
The sound field on the xy plane is reproduced using the secondary sound source circle arranged
in the reproduction area from the sound pressure distribution acquired by the sound receiving
circle arranged in the sound collection area.
[0102]
A synthetic sound field Psyn (r <->, ω) by secondary sound sources continuously arranged on the
circumference can be written as follows in the circular harmonic spectrum region as in the case
of the first embodiment.
[0103]
[0104]
On the other hand, the sound pressure distribution P (Rm, π / 2, φ) obtained on the
circumference of the radius Rm of the sound collection field Prcv (r <->, ω) of the target sound
03-05-2019
23
field Pdes (r <->, ω) , ω) is required to be represented.
Assuming that a rigid sphere with radius Rb (≦ Rm) is installed at the same position and center
as the receiving circle, the sound collection field Prcv (r <−>, ω) is the incident sound field Pinc
(r <−>, It can be expressed by the sum of ω) and the scattered sound field Psct (r <−>, ω).
Prcv (r <->, ω) = Pinc (r <->, ω) + Psct (r <->, ω) (38) Also, according to the boundary condition
on a hard sphere,
[0105]
[0106]
Is true.
Also, Pinc (r <->, ω) and Psct (r <->, ω) can be written as follows in the spherical harmonic
spectrum region.
[0107]
[0108]
Here, Y <m> n (θ, φ) represents a spherical harmonic function.
したがって、
[0109]
[0110]
03-05-2019
24
となる。
From the above, assuming that the sound collection field is universal in the z-axis direction, the
relational expression between the incident sound field and the sound collection field can be
derived as follows.
[0111]
[0112]
Furthermore,
[0113]
[0114]
であり、
[0115]
[0116]
であることから、
[0117]
[0118]
となる。
Since it is sufficient if the synthetic sound field Psys (r <->, ω) and the target sound field Pdes (r
03-05-2019
25
<->, ω) coincide with each other,
[0119]
[0120]
Here, for simplicity, it is assumed that G (r <->-r <-> s, ω) is a monopole characteristic.
[0121]
[0122]
As described above, the conversion equation of the secondary sound source drive signal is
obtained from the sound pressure distribution on the sound receiving circle, but it is necessary to
give in advance a circle whose amplitude matches the target sound field as r = Rref.
[0123]
Assuming that the secondary sound source is a line sound source, the conversion equation can be
further simplified.
[0124]
[0125]
であることより、
[0126]
[0127]
となる。
However, an actual speaker is close to monopole characteristics, and a correction for linear
03-05-2019
26
sound source approximation is required.
From the equation (26), the following frequency characteristics are corrected for each output
signal.
[0128]
[0129]
In the case of Rb = Rm, it can be derived using the following relational expression.
[0130]
[0131]
[Modifications, Etc.] Each part constituting the sound field sound collecting and reproducing
apparatus may be provided in either the sound collecting apparatus arranged in the first space or
the reproduction apparatus arranged in the second space.
In other words, the processing of each of the frequency conversion unit 1, the space frequency
conversion unit 3, the conversion filter unit 4, the space frequency inverse conversion unit 5, and
the frequency inversion unit 6 is performed by the sound collection device disposed in the first
space. It may be executed or may be executed by a playback device located in the second space.
The signal generated by the sound collection device is transmitted to the reproduction device.
[0132]
The positions of the first space and the second space are not limited to those shown in FIGS. 1
and 4.
03-05-2019
27
The first space and the second space may be adjacent to or separated from each other.
Also, the orientation of the first space and the second space may be any.
[0133]
As long as the sound field sound collecting and reproducing apparatus includes the conversion
filter unit 4, it may not include other units.
For example, the sound field sound collecting and reproducing apparatus may be configured of
the conversion filter unit 4, the spatial frequency inverse conversion unit 5, and the frequency
inverse conversion unit 6.
Further, the sound field sound collecting and reproducing apparatus may be configured of the
frequency conversion unit 1, the spatial frequency conversion unit 3, and the conversion filter
unit 4.
[0134]
The processing of the frequency conversion unit 1 and the processing of the spatial frequency
conversion unit 3 may be performed simultaneously.
Similarly, the process of the spatial frequency inverse transform unit 5 and the process of the
frequency inverse transform unit 6 may be performed simultaneously.
Further, the space frequency conversion unit 3 and the space frequency inverse conversion unit
5 may be interchanged.
[0135]
03-05-2019
28
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.
[0136]
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.
[0137]
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.
[0138]
Reference Signs List 1 frequency conversion unit 3 space frequency conversion unit 4 conversion
filter unit 5 space frequency inverse conversion unit 6 frequency inverse conversion unit
03-05-2019
29
Документ
Категория
Без категории
Просмотров
0
Размер файла
41 Кб
Теги
jp2014150416
1/--страниц
Пожаловаться на содержимое документа