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DESCRIPTION JP2015198412

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DESCRIPTION JP2015198412
The present invention provides a converter capable of simultaneously analyzing waves arriving
from various directions with high spatial resolution and shortening an impulse response length
between a wave source and an observation point. SOLUTION: A converting apparatus
corresponds to N n-th high SN zone forming devices forming N high SN zones, N being an integer
of 2 or more, n = 1, 2, ..., N, and M corresponding to n. , M, and includes (波 M) m-th conversion
units capable of converting a wave to a signal or a signal to a wave. The Mth m-th conversion
unit is arranged near the high SN zone of the n-th high SN zone formation device, and the waves
converted by the (ΣM) m-th conversion units or the converted waves are all the same And at
least one of the (ΣM) conversion units is disposed at a position other than the high SN zone
formed by the n-th high SN zone former corresponding to the m-th conversion unit. There is.
[Selected figure] Figure 17
Converter
[0001]
The present invention relates to a conversion technique for converting a wave to a signal or a
signal to a wave. Here, the waves include sound waves and electromagnetic waves. Sound waves
have a frequency of about 20 to 20 kHz. The electromagnetic waves include light waves, radio
waves, and the like. The light waves are electromagnetic waves having a wavelength of about
400 to 750 nm (frequency: 750 THz to 400 THz), and the radio waves are electromagnetic
waves having a frequency of about 3 THz or less. Further, the signal referred to here is a
symbolized and encoded in order to transmit information, and the medium may be electricity,
sound, light, radio waves or the like.
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[0002]
Non-patent documents 1, 2 and 3 are known as prior art of conversion technology.
[0003]
In Non-Patent Document 1, interference noise removal is realized using an array in which sensors
are installed at high SN zone positions of parabolic reflectors.
The noise removal performance depends on the number of parabola devices constituting the
array.
[0004]
In Non-Patent Documents 2 and 3, a pseudo diffuse sound field is generated by a reflective
structure, and a microphone array is installed therein to realize diffuse sensing.
[0005]
「2013
May 07 The summit facility installation of 16 satellite antennas made by ALMA telescope is
completed, [online], ALMA NAOJ, [search on February 26, 2014], Internet <http: //alma.mtk.nao
.ac.jp / j / news / pressrelease / 201305077095.html> K. Niwa, S. Sakauchi, K. Furuya, M.
Okamoto, and Y. Haneda, "Diffused sensing for sharp directivity microphone array", ICASSP
2012, 2012 , pp.
225 -228 K. Niwa, Y. Hioka, K. Furuya, and Y. Haneda, "Telescopic microphone array using
reflector for segmentation target from noises in the same direction", ICASSP 2012, 2012, pp.
5457-5460
[0006]
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2
However, in Non-Patent Document 1, although it is an array optimized for one direction, it is not
possible to simultaneously analyze information coming from various directions. When analyzing
information coming from other directions, it is necessary to change the orientation of the
parabola device.
[0007]
In Non-Patent Documents 2 and 3, by installing an array in a diffuse sound field, correlation
between channels can be reduced, and sounds arriving from various directions can be
simultaneously analyzed with high spatial resolution. However, since the array is placed in the
diffuse sound field, the impulse response length becomes long. As the impulse response length
becomes longer, the filter length tends to be naturally longer, which causes problems such as an
increase in processing delay and an increase in filter instability. In addition, the design itself
becomes complicated, and the amount of calculation at the time of filtering becomes large.
[0008]
An object of the present invention is to provide a converter which can simultaneously analyze
waves arriving from various directions with high spatial resolution and shorten the impulse
response length between the wave source and the observation point.
[0009]
In order to solve the above problem, according to one aspect of the present invention, the
conversion device sets N to an integer of 2 or more, n = 1, 2,. An n-th high SN zone former, M n is
an integer of 1 or more corresponding to n, m n = 1,..., M n, and waves can be converted into
signals or signals can be converted into waves (Σ n = 1 And <N> Mn> pieces of m <n>
conversion units.
M n pieces of m n conversion units are arranged near the high SN zone of the n-th high SN zone
formation unit, and waves converted by ((n = 1 <N> M n) pieces of m n conversion units
Alternatively, all the converted waves are waves of the same type, and at least one of the (m n)
conversion units of (Σ n = 1 <N> M n) corresponds to the m n conversion unit Are disposed at
positions other than the high SN zone formed by the n-th high SN zone former.
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[0010]
According to the present invention, (1) waves arriving from various directions can be analyzed
simultaneously, (2) (i) impulse response is short, (ii) transmit / receive energy is high, (iii) interchannel correlation is low The effect of enabling transmission and reception of signals satisfying
the three conditions is achieved.
[0011]
The figure for demonstrating the conditions of a sound collection apparatus.
The figure which shows the parabola antenna, an antenna element, and the example of
arrangement | positioning. The figure for demonstrating the area with high SN ratio in case an
electromagnetic wave comes from the direction different from a predetermined direction. The
figure which shows the function structure of the sound collection apparatus which concerns on
1st embodiment. The figure which shows the example of the processing flow of the sound
collection apparatus which concerns on 1st embodiment. The figure which shows the example of
arrangement | positioning of the microphone with respect to a high SN zone formation device.
The figure which shows the example of arrangement | positioning of the microphone with
respect to a high SN zone formation device. The figure for demonstrating the range of "high SN
zone vicinity." The figure for demonstrating the range of "high SN zone vicinity." The figure for
demonstrating the vicinity of a surface similar to a high SN zone formation surface. The figure for
demonstrating the method to measure a transfer characteristic. The figure for demonstrating the
range of "high SN zone vicinity" at the time of using a lens. FIG. 7 is a diagram showing a
functional configuration of a reproduction device according to a second embodiment. The figure
which shows the example of the processing flow of the reproducing | regenerating apparatus
concerning 2nd embodiment. The figure for demonstrating the positional relationship of the
microphone with respect to the high SN zone formation device in 3rd embodiment. The figure
which shows the function structure of the sound collection apparatus which concerns on 3rd
embodiment. The figure which shows the example of arrangement | positioning of the
microphone with respect to a high SN zone formation device. The figure which shows the
example of arrangement | positioning of the microphone with respect to a high SN zone
formation device.
[0012]
Hereinafter, embodiments of the present invention will be described. In the drawings used in the
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following description, the same reference numerals are given to constituent parts having the
same functions and steps for performing the same processing, and redundant description will be
omitted. In the following description, a symbol “<→>” or the like used in the text should be
written directly above the preceding character, but due to the restriction of the text notation, it is
written immediately after the character. 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.
[0013]
First Embodiment In this embodiment, an example in which the present invention is applied to a
conversion technique for converting waves into signals will be described. The following
techniques are mentioned as an example of the conversion technique which converts a wave into
a signal. (1)There are techniques for converting sound waves into electrical signals and (2)
techniques for converting electromagnetic waves into electrical signals. However, the present
invention is not limited to this, and (3) a technique for converting sound waves into optical
signals may be used. (1)There is a microphone as a device to realize. (2)There is a receiving
antenna as a device to realize. Also, if there is hardware that can directly realize (3), it may be
used.
[0014]
In particular, in the present embodiment, a case will be described in which sound waves are used
as waves and a plurality of microphones (microphone arrays) that convert sound waves into
electric signals are used as the plurality of conversion units.
[0015]
First, the sound collecting process based on the diffusion sensing described so far in Non-Patent
Document 2 will be described.
[0016]
[Modeling of Observation Signal] Consider a situation in which one target sound and K (≧ 1)
pieces of noise are received using M (≧ 2) microphones.
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The purpose is directed control that emphasizes the target sound at any position in the presence
of a lot of noise.
The goal is achieved by suppressing the K noise sources and emphasizing the target sound. The
impulse response between the m (m = 1, 2,..., M) th microphone and the target sound and the k (k
= 1, 2,..., K) noise is am (i), bk, m respectively (i) However, let L be the impulse response length,
and i = 0, 1,. The impulse response length L may be determined experimentally according to the
reverberation time determined by the size and structure of the device and the condition of the
installed room. When the sound source signals of the target sound and the k-th noise are s (t) and
n k (t), the observed signal x m (t) observed by the m-th microphone is modeled by the following
equation.
[0017]
Here, t represents an index of time.
[0018]
By short-time Fourier transforming x m (t), the convolutional mixture of equation (1) is
approximated as an instantaneous mixture in the frequency domain as in the following equation.
[0019]
[0020]
Here, ω and τ respectively indicate the frequency and the index of the frame.
Also, X m (ω, τ), S (ω, τ), N k (ω, τ) are the observation signal x m (t), the source signal s (t)
of the target sound, and the k th noise source 2 represents a time-frequency representation of
the signal nk (t).
a m (ω) and b k, m (ω) represent the frequency characteristics between the target sound and the
k-th noise and the m-th microphone, respectively, and these are hereinafter referred to as
transfer characteristics.
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Expressing equation (2) in matrix form, it becomes as follows.
[0021]
And <T> represents transposition.
[0022]
[Beamforming] The output signal y (t) after beamforming is obtained by convolving the
observation signal xm (t) with the filter wm (t) designed to enhance the target sound as in the
following equation Be
[0023]
[0024]
Here, J represents the filter length, and may be approximately the same as the impulse response
length L.
Y (ω, τ) which is a time-frequency expression of y (t) can be approximately obtained by the
following equation.
[0025]
[0026]
Here, <H> represents a conjugate transpose, and the complex conjugate of W m (ω) corresponds
to the frequency response of w m (j).
[0027]
[0028]
When the noise component contained in the output signal Y (ω, τ) is written as Y N (ω, τ), the
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power p N (ω) of the following equation is defined as the power of the noise component.
[0029]
[0030]
Here, E T represents temporal expected value calculation.
Assuming that the source signals are uncorrelated with each other, the power p N (ω) can be
calculated only by the transfer characteristic b <→> k (ω) and the filter W <→> (ω).
[0031]
[0032]
In the field of array signal processing, various filter design methods have been described to
minimize p N (ω).
The delay-sum method and the maximum likelihood method will be described as a representative
example (see reference 1).
[Reference 1] Asano, "Array signal processing of sound-low order, tracking and separation of
sound source", Corona Co., 2011 In the delay-and-sum method, the filter W <→> DS is a target
sound directly according to the following equation Designed to emphasize the sound.
[0033]
Represents the array manifold vector of the direct sound of the target sound.
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The element hm (ω) represents the transfer characteristic of the direct sound path from the
target sound to the mth microphone, where dm is the distance between the target sound and the
mth microphone, c is the speed of sound, and j is the imaginary unit. For example, it can be
calculated by the following equation.
[0034]
[0035]
Also, in the maximum likelihood method, the filter W <->> ML is designed to emphasize the direct
sound of the target sound and minimize the power p N (ω) according to the following equation.
[0036]
[0037]
Here, R (ω) represents a spatial correlation matrix of noise.
For example, assuming that there is no correlation between sound source signals, the spatial
correlation matrix R (ω) of noise is calculated using only the transfer characteristic b <→> k (ω)
as in the following equation.
[0038]
[0039]
In classical array signal processing as described in reference 1, it has been considered how to
arrange the spacing between microphones.
However, the correlation between microphones is often high except for specific frequencies.
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The following two are known as representative problems.
The first problem is that it is difficult to perform narrow pointing control because the correlation
between transfer characteristics tends to be high in a low frequency band with a long
wavelength.
The second problem is that in the high frequency band where the wavelength is short, spatial
aliasing occurs that emphasizes the sound other than the specific target sound unless the
microphones are arranged at an interval equal to or less than a half wavelength of the
wavelength.
From the above two points, it has been difficult to reduce the power p N (ω) over a wide band.
[0040]
[Diffusion Sensing] In Non-Patent Document 2, in order to reduce the power p N (ω) over a wide
band, what kind of nature of the transfer characteristic should be considered and summarized as
diffusion sensing.
[0041]
In diffusion sensing, by devising the array structure, the transfer characteristics themselves are
physically changed so as to be uncorrelated with each other as expressed by the following
equation.
[0042]
[0043]
Here, any physical means for changing the nature of the transfer characteristic itself can be used.
For example, by placing a reflective structure in the vicinity of the microphone, the transfer
characteristic itself changes.
The method proposed in Non-Patent Document 2 is a method in which reflection is repeated
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many times, a sound field (pseudo-diffuse sound field) where reflected sound arrives isotropically
is generated, and a microphone array is installed therein. .
For example, if a reflecting structure shaped to surround the microphone array is made and
opened only on one side, the sound arriving inside the reflecting structure will naturally be
repeatedly reflected to generate a pseudo diffuse sound field.
[0044]
It will be briefly explained why the transfer characteristics are de-correlated if the microphone
array is installed in the diffuse sound field.
Assuming that the correlation between transfer characteristics is γ (ω), it is known that the
correlation γ (ω) in the diffuse sound field is calculated by the following equation.
[0045]
[0046]
Here, E S and p <→> respectively represent spatial expectation value calculations and position
vectors between microphones.
Assuming that the distance between the microphones || p <→> || is sufficiently wide, the
expected value of the correlation γ (ω) between the transfer characteristics in the diffuse sound
field approaches 0.
[0047]
[0048]
Therefore, in the prior art, a pseudo diffuse sound field is physically generated by a reflective
structure, and a microphone array is installed therein (see non-patent documents 2 and 3).
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[0049]
Also, in order to reduce the power p N (ω), a filter design method using transfer characteristics
prepared by prior simulation and measurement has been studied.
Simply put, it has been designed to emphasize only the target sound, but in diffuse sensing based
control it is designed to emphasize the transfer characteristic itself.
[0050]
When the delay-sum method is based, the filter W <→> is realized by replacing the array
manifold vector h <→> (ω) with the target sound transfer characteristic a <→> (ω) as in the
following equation. Can design DS1 (ω).
[0051]
[0052]
In this case, it is necessary to prepare a <→> (ω) in advance by simulation or measurement.
[0053]
Moreover, when based on the maximum likelihood method, the filter W <→> DS2 (ω) can be
designed by the following equation.
[0054]
Also in this case, it is necessary to prepare a <→> (ω) and R (ω) in advance by simulation and
measurement.
When generating a pseudo-diffuse sound field using the means mentioned above and collecting
the sound, it is expected that the transfer characteristic is naturally uncorrelated, so the power p
N (ω ) Could be reduced over a wide band.
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[0055]
<Point of First Embodiment> In the zoom-up microphones of Non-Patent Documents 2 and 3, the
sound structure (pseudo-diffuse sound field) in which the sound wave is reflected many times by
the reflecting structure and the reflected sound arrives isotropically. Since the generation is
performed and the array is placed therein, the impulse response length becomes long, and
accordingly the filter length becomes long, and the occurrence of processing delay and the
instability of the filter increase.
[0056]
In the present embodiment, the idea of reducing inter-channel correlation in the zoom-up
microphones of Non-Patent Documents 2 and 3 is inherited, and the SN ratio at the time of sound
reception is increased while maintaining a short impulse response length.
With such a configuration, it is possible to analyze information coming from various directions
stably and simultaneously with high spatial resolution.
[0057]
In the present embodiment, in order to increase the SN ratio at the time of sound reception, a
high SN zone formation device is used to form a high SN zone, and a plurality of microphones are
arranged near the high SN zone.
At this time, in order to reduce inter-channel correlation, the microphones are arranged at
different positions (locations) near the high SN zone.
The high SN zone is a range in which the SN ratio is particularly enhanced by the high SN zone
former, and for example, when the high SN zone former is a parabolic reflector, it is a focal point
formed by the parabolic reflector. .
The vicinity of the high SN zone means a range where the SN ratio increases when the high SN
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zone former is present as compared to when the high SN zone former is absent.
Therefore, naturally, the high SN zone is included, but the range in which the SN ratio is
increased is included although not as high as the high SN zone.
[0058]
The conditions of the sound collection device defined in the present embodiment will be
described with reference to FIG.
[0059]
[Required Conditions] (1) Including one or more high SN zoners 190 to include a high SN zoner
to form a high SN zone.
The high SN zone former 190 forms a high SN zone F for sound waves.
For example, a concave structure composed of a rigid body is used as the high SN zone former
190.
A parabolic reflector can be considered as one of the concave structures. The minimum required
number of high SN zone formation units 190 is one.
[0060]
(2)
It includes M microphones 211-m including a plurality of microphones disposed at different
positions near the high SN zone FE. Here, M is an integer of 2 or more, and m = 1, 2,. The
microphone 211-m is disposed in the vicinity of the high SN zone FE, and the microphone 211-m
and the microphone 211-m ′ are disposed at different positions. However, m 'is one of 1, 2, ...,
M, and m ≠ m'. The minimum number of microphones 211-m is two.
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[0061]
(3)
Including a Filtering Unit Having a filtering unit 160 capable of filtering independently for M
microphones. Furthermore, the filtering unit 160 performs signal processing to control not only
the direct wave but also the transfer characteristic itself including the reflected wave.
[0062]
<Summary of First Embodiment> In general, the parabolic antenna 90 having a reflector with a
parabolic curved surface arranges the antenna element 91 at the focal point F on the assumption
that radio waves come from one direction (for example, the front direction). (See Figure 2). With
such a configuration, radio waves can be received not from points but from the surface, and the
SN ratio can be increased.
[0063]
When radio waves come from other directions, an area Q with a high SN ratio occurs near the
focal point (see FIG. 3). Such a property is not limited to the parabolic antenna, and a similar
property appears in the case of forming a focal point of a sound wave by providing a concave
reflection portion. In this embodiment, by utilizing such a property in the vicinity of a high SN
zone such as a focal point, a plurality of microphones are arranged in the vicinity of a high SN
zone such as a focal point to increase the SN ratio.
[0064]
Further, inter-channel correlation is reduced by arranging the microphones 211-m and the
microphones 211-m ′ at different positions. When a plurality of microphones are arranged at
the focal point, although the SN ratio is high, the correlation between channels becomes very
high, so radio waves coming from various directions can not be received, and radio waves coming
from one direction Can be received with high accuracy.
[0065]
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Note that raising the SN ratio means making the diagonal component of the spatial correlation
matrix R a large value. However, assuming that the observation signal collected by the
microphone 211-m is X m, the mm ′ component of the spatial correlation matrix R is R mm ′ =
E [X m x m ′ <H>]. Here, m = 1, 2, ..., M, m '= 1, 2, ..., M, and when m = m', it becomes a diagonal
component of the spatial correlation matrix R and R mm = which is a diagonal component E
[XmXm <H>] represents the received energy (power) of the microphone 211-m. E [•] represents
expected value calculation. On the other hand, reducing inter-channel correlation means making
non-diagonal components of the spatial correlation matrix R small. Satisfying the two conditions
simultaneously corresponds to maximizing the determinant det (R) of the spatial correlation
matrix R. .
[0066]
In this embodiment, a plurality of microphones are arranged at different positions near the high
SN zone so as to maximize the determinant det (R). Furthermore, in the present embodiment, in
order to shorten the impulse response length, in other words, in order to shorten the filter length
used in the filtering unit, the high SN zone formation unit 190 is configured such that the
number of sound wave reflections is one to two. Form to be a degree. Also, in terms of time, the
shape of the high SN zone formation unit 190 is formed so that the difference in arrival time of
the direct sound and the main reflected wave to the microphone is within 50 ms. For example,
the shape is parabolic.
[0067]
<Sound Collection Device 10 According to First Embodiment> [Signal Processing of Sound
Collection Device 10] The functional configuration and processing flow of the sound collection
device 10 according to the first embodiment are shown in FIG. 4 and FIG. The sound collection
device 10 according to the first embodiment includes M microphones 211-m, an AD conversion
unit 120, a frequency domain conversion unit 130, a filtering unit 160, a time domain
conversion unit 170, a filter calculation unit 150, and a transfer characteristic storage unit. 140,
including a high SN zoner 190; m=1,2,…,Mであり、M≧2である。
[0068]
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High SN Zoner 190 The high SN zoner 190 forms a high SN zone for waves in a predetermined
direction. The high SN zone former 190 has a high SN zone formation surface to form a high SN
zone. The high SN zone forming surface has a shape, a material, and a size capable of reflecting a
sound wave, and a high SN zone is formed by reflecting the sound wave. In this embodiment, the
high SN zone former 190 is a parabola shaped rigid body, and the inner surface of the parabola
shape corresponds to the high SN zone forming plane. Therefore, the focus formed by the
parabolic shape corresponds to the SN zone, and the vicinity of the focus corresponds to the
vicinity of the SN zone. It is desirable that the diameter of the circle formed by the edge of the
parabola shape be equal to or larger than a half wavelength of the maximum wavelength width
among the wavelength widths to be handled. Therefore, since the wavelength width handled by
the wavelength of the sound wave is 0.01 to 1 m, it is preferable that the diameter of the circle
formed by the edge of the parabolic shape be about 0.5 m or more. The material of the high SN
zone forming unit 190 is preferably a material that easily reflects sound waves (in other words, a
material having a high reflection coefficient), and a hard material is preferable. Therefore, in the
present embodiment, a hard and area-shaped parabolic rigid body is used as the high SN zone
forming unit 190.
[0069]
<Microphone 211-m> M microphones 211-m are used to collect sound (s1), and an analog signal
(sound collection signal) is output to the AD conversion unit 120. The microphones 211-m and
the microphones 211-m ′ are disposed at different positions near the high SN zone formed by
the high SN zone former 190. Here, m 'is one of 1, 2, ..., M, and m'm'.
[0070]
<Positions of Microphones 211-m for High SN Zone Forming Unit 190> M microphones may be
arranged such that the determinant det (R) of the spatial correlation matrix R is maximized. M
microphones are placed near the high SN zone to increase the signal-to-noise ratio. Also, M
microphones are placed at different positions so that the inter-channel correlation is low. In other
words, the M microphones may be arranged such that the correlation between sound waves
converted into electric signals by the M microphones is low. As a whole, it is desirable to arrange
M microphones so that the correlation is low, but if M microphones 211-m are arranged so that
at least one correlation becomes low, an effect can be obtained . In other words, the combination
of correlations between sound waves converted by any two microphones out of M microphones
is considered MC 2, but at least one of the combinations of correlations MC 2 The M
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microphones 211-m may be arranged such that one correlation is low.
[0071]
6 and 7 each show an example of the arrangement of the microphones 211-m with respect to the
high SN zone former 190.
[0072]
In this embodiment, the microphone 211-m is supported by the support portion 191 having a
shape that does not easily block the wave that arrives at the high SN zone formation unit 190.
[0073]
In FIG. 6, the support portion 191 is a structure including a surface located in the vicinity of the
high SN zone formed by the high SN zone formation unit 190, and a hole for holding the
microphone 211-m is on the surface. Multiple are formed.
For example, M ′ (M ′> M) holes are formed, and each microphone 211-m is embedded in any
of M ′ holes.
In this embodiment, the support portion 191 includes a mesh member 191A and a support
member 191B. The support member 191B is a rod-like structure that forms each side extending
from the top of the square of a square pyramid having the top of the bottom of the parabolic
high SN zone former 190 as the top. The mesh member 191A is provided in the same plane as
the bottom of the square pyramid. The support member 191 B couples the high SN zone former
190 with the mesh member 191 A and secures the mesh 191 A to the high SN zone former 190.
The mesh member 191A is a structure including a surface located in the vicinity of the high SN
zone formed by the high SN zone former 190. Furthermore, a plurality of holes for holding the
microphone 211-m are formed in the mesh member 191A. In other words, the M microphones
211-m can be embedded in any of the meshes of the mesh member 191A.
[0074]
In FIG. 7, the support portion 191 is a rod-like structure that couples the high SN zone former
190 and the microphone 211-m.
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[0075]
The shape of the support portion 191 is not limited to the above-described one, and may be any
shape that does not easily block the wave arriving at the high SN zone forming device 190 and
that can support the microphone 211-m. It is also good.
[0076]
The “near high SN zone” will be described.
The high SN zone means, as described above, a high SN zone (for example, a focal point) which
the high SN zone former 190 forms for a wave in a predetermined direction.
For example, the high SN zoner 190 is recessed to form a high SN zone. In the direction
perpendicular to the predetermined direction, the range “near the high SN zone” means the
inside of the concave edge (see FIGS. 8 and 9). Due to the positional relationship between the
concave edge and the high SN zone, the range of “near the high SN zone” in a predetermined
direction is different. The distance between the plane H formed by the concave edge and the
plane I passing through the bottom of the concave formed by the high SN zone generator 190 is
HI, and the plane I through the concave bottom formed by the high SN zone F and the high SN
zone 190 (1) When HI 型 FI, the range from “near high SN zone” in the predetermined
direction is from the bottom of the concave to 2HI in the predetermined direction (see FIG. 8).
[0077]
(2)When HI <FI, the area from the bottom of the concave to 2FI in a predetermined direction is
the “near high SN zone” range in a predetermined direction (see FIG. 9).
[0078]
However, even if the concave is concave so as to form a high SN zone, the surface formed by the
edge is not necessarily a plane, and the high SN zone (for example, focal point) is not a strict
point, Since it has a certain range, “in the vicinity of the high SN zone” means a range in which
the SN ratio is higher in some cases than in the case where the high SN zone former 190 is not
provided.
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[0079]
In the vicinity of the high SN zone, in particular, in the vicinity J′E of the surface J ′ similar to
the high SN zone forming surface J, the SN ratio is high (FIG. 10). By arranging the microphones
211-m, it is possible to more appropriately maximize the determinant det (R) of the spatial
correlation matrix R.
In addition, the vicinity J'E of the face J 'of the similar shape may be said to be on the face having
the similar shape to the high SN zone forming face J, or the vicinity of the face having the similar
shape to the high SN zone forming face. It is also good.
The point is that the M microphones 211-m may be disposed in the vicinity of the high SN zone
where the SN ratio is high, particularly at different positions in the range where the SN ratio is
considered to be high.
[0080]
<AD Converting Unit 120> The AD converting unit 120 converts the M analog signals collected
by the M microphones 211-m into digital signals x <→> (t) = [x 1 (t),. Convert to M (t)] <T> (s 2),
and output to the frequency domain conversion unit 130. t represents an index of discrete time.
[0081]
<Frequency domain converter 130> The frequency domain converter 130 first receives the
digital signal x <→> (t) = [x 1 (t), ..., x M (t)] <T output from the AD converter 120. Input N
samples in the buffer for each channel and input a digital signal in frame units x <→> (τ) = [x
<→> 1 (τ), ..., x <→> M (τ)] < Generate T>. τ is the index of the frame number. x <→> m (τ) =
[x m ((τ−1) N + 1),..., x m (τN)] (1 ≦ m ≦ M). Although N depends on the sampling frequency,
2048 points are appropriate for 48 kHz sampling. Next, the frequency domain conversion unit
130 converts the digital signal x <→> (τ) of each frame into a signal X <→> (ω, τ) = [X 1 (ω,
τ),. Convert to ω, τ)] <T> (s 3) and output. ω is the index of the discrete frequency. Although
there is a fast discrete Fourier transform as one of the methods for converting time domain
signals into frequency domain signals, the present invention is not limited to this, and other
methods for converting into frequency domain signals may be used. The frequency domain signal
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X <→> (ω, τ) is output for each frequency ω and frame τ.
[0082]
<Transmission Characteristic Storage Unit 140> The transmission characteristic storage unit 140
is a transmission characteristic A <→> (ω) = [a <→> (ω), b <→> 1 (measured in advance using
the sound collection device 10) Store ω), ..., b <→> K (ω)]. a <→> (ω) = [a 1 (ω), ..., a M (ω)] <T>
is the transfer characteristic at the frequency ω between the target sound and the M
microphones, in other words, It is assumed that a <→> (ω) = [a 1 (ω),..., a M (ω)] <T> is a
transfer characteristic of the target sound to each microphone included in the microphone array
at the frequency ω. k = 1, 2,..., K, and K is the number of noises, bk <→> (ω) = [b k1 (ω),..., b kM
(ω)] <T> Of the microphone at a frequency ω, in other words, bk <→> (ω) = [b k1 (ω), ..., b kM
(ω)] <T> is the microphone array Of the noise k to each of the microphones included in the
frequency .omega. Note that the transfer characteristic A <→> (ω) may be prepared in advance
by a theoretical formula or simulation, not by prior measurement.
[0083]
For example, as shown in FIG. 11, the speaker array 95 on the rail 94 is moved to the left and
right, and the transfer characteristic at each position is measured. Furthermore, the rail 94 may
be moved back and forth to measure the transfer characteristic at each position. Although a
plurality of high SN zone formers 190 are used in FIG. 11, only one high SN zone former 190
may be used. The transfer characteristics may be measured in advance in the same situation as
the usage situation (same number, same arrangement, same high SN zone former 190 and M
same arrangement, same microphone 211-m). At this time, M microphones 211-m may be
arranged for one high SN zone former 190 so that the determinant det (R) of the spatial
correlation matrix R is maximized.
[0084]
<Filter Calculation Unit 150> The filter calculation unit 150 takes out the transfer characteristic
A <→> (ω) from the transfer characteristic storage unit 140, calculates the filter W <→> (ω),
and outputs it to the filtering unit 160. For example, a filter W <> →> (ω) used for signal
processing to suppress an acoustic signal from a specific position or direction is calculated.
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[0085]
The main point of the beamforming technology of this embodiment is to arrange a plurality of
microphones in the vicinity of the high SN zone to enhance the SN ratio, and arrange a plurality
of microphones in different positions in the vicinity of the high SN zone. To uncorrelate.
Therefore, since the filter design concept itself is not affected, the filter W <> →> (ω) can be
designed by the same method as the prior art. For example, the filter design method according to
<1> SN ratio maximization criteria described in reference 2; <2> filter design method based on
Power Inversion; <3> one or more blind spots (of noise Filter design method by the minimum
variance non-distortion response method with the constraint condition of gain suppression), <4>
filter design method by delay-and-sum beam forming method, <5> maximum likelihood method
The filter W <→> (ω) can be designed by a filter design method, <6> AMNOR (Adaptive
Microphone-array for noise reduction) method, or the like. [Reference 2] International
Publication No. WO 2012/086834 Pamphlet
[0086]
For example, when based on the delay-and-sum method, the filter W <→> DS1 (ω) is calculated
by the equation (16).
[0087]
[0088]
Further, for example, when the maximum likelihood method is used as a base, the filter W <→>
DS2 (ω) is calculated by Expression (17).
[0089]
[0090]
Also, for example, in the case of a filter design method based on the minimum variance nodistortion response method having one or more dead angles as constraint conditions, the filter W
<→> DS3 (ω) is calculated by the following equation.
[0091]
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22
[0092]
Here, f s (ω) and f k (ω) represent the pass characteristics at the frequency ω with respect to
the target sound and noise k (k = 1, 2,..., K).
For example, in equation (18), when it can be prepared in advance as the transfer characteristic a
<→> (ω) dependent on the direction θ (ω, θ), the transfer characteristic a <→> ( The filter W
<→> (ω, θ) is calculated using ω, θ), and the filtering unit 160 can perform signal processing
in a specific direction θ s.
Also, if the transfer characteristic a <→> (ω) can be prepared in advance as the transfer
characteristic a <→> (ω, θ, D) depending on the direction θ and the distance D, the transfer
characteristic a <→> (ω , θ, D) to calculate the filter W → → (ω, θ, D), and the filtering unit
160 outputs a signal at a specific position (a position specified by a specific direction θ s and a
distance DH) Processing can be done.
[0093]
<Filtering unit 160> The filtering unit 160 receives the filter W <→> (ω) in advance from the
filter calculation unit 150, receives the frequency domain signal X <→> (ω, τ), and transmits
each frequency for each frame τ. For ω ∈ Ω, filter W <→> (ω) to frequency domain signal X
<→> (ω, τ) = [X 1 (ω, τ), ..., XM (ω, τ)] <T> Applying (refer to equation (5), s4), the output
signal Y (ω, τ) is output.
[0094]
[0095]
For example, the filtering unit 160 makes the sound collection characteristics of the sound signal
emitted from at least a plurality of positions or directions in space different based on the sound
collection signal by the microphone 211-m and the sound collection signal by the microphone
211-m ′. What is necessary.
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“Making the sound collection characteristics different” means, for example, locally collecting
the sound signal emitted at a specific position and suppressing sound collection of sound signals
emitted at other positions as much as possible. It means that the sound signal emitted at a
position is suppressed (silenced) to pick up only the sound signal emitted at other positions.
[0096]
<Time Domain Transforming Unit 170> The time domain transforming unit 170 transforms the
output signal Y (ω, τ) of each frequency ω∈Ω of the τ frame into the time domain (s5), and
the frame unit time of the τ frame A domain signal y (τ) is obtained, and further, the obtained
frame unit time domain signal y (τ) is connected in the order of the index of the frame number
to output a time domain signal y (t).
The method of converting the frequency domain signal into the time domain signal is an inverse
conversion corresponding to the conversion method used in the process of s3, and is, for
example, high-speed discrete inverse Fourier transform.
[0097]
<Effect> By inheriting the idea of reducing the inter-channel correlation in the zoom-up
microphones of Non-Patent Documents 1 and 2 with such a configuration, it is possible to further
shorten the impulse response length and increase the SN ratio at the time of sound reception. it
can.
Therefore, it is possible to analyze waves coming from various directions (further, information
indicated by the waves) stably, simultaneously, with high spatial resolution.
For example, arbitrary directional control can be performed over a wide band by performing
appropriate signal processing using a filter using a transfer characteristic prepared in advance.
In this embodiment, the filter W <→> (ω) is calculated in advance, but the filter calculation unit
150 is performed after the sound source position and the arrangement of the microphones are
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24
determined according to the calculation processing capability of the sound collection device 10
or the like. May be configured to calculate the filter W <→> (ω) for each frequency.
[0098]
<Modifications> In the present embodiment, a sound wave is used as a wave, but a radio wave or
a light wave may be used, or an electromagnetic wave of another band may be used.
In that case, a receiving antenna, a light receiving element or the like can be used instead of the
microphone. The point is that a plurality of conversion units capable of converting waves of the
same type into signals may be used. In other words, the waves to be converted in the M
conversion units may be waves of the same type. The converter may be called a receiver in the
sense that it can receive waves. Moreover, you may call it a wave source input part in the
meaning of making the wave transmitted from a wave source (sound source) into an input.
[0099]
The high SN zone former 190 may be realized by a wall, a floor, a ceiling, an iron plate, a hard
ball (a ball made of a rigid body (for example, metal such as iron or resin)). The point is that any
high SN zone can be formed for waves in a predetermined direction. However, it is desirable that
the number of reflections of the sound wave in the vicinity of the high SN zone is about 1 to 2 so
that the reverberation time does not become too long. Therefore, the high SN zone former 190 is
not necessarily required to have a parabola shape, but as described above, it is desirable that the
high SN zone former 190 be a concave (e.g., bowl-like) having a depression and a shape where
reflected sound concentrates. Furthermore, it is desirable that the concave edges (ends) not face
inwards (outwardly) so that the reverberation time does not become too long. For example, if the
high SN zone former 190 consists of a part of a sphere, it is below the hemisphere.
[0100]
For example, when radio waves are used as waves, the high SN zone formation unit 190 may
form a high SN zone for radio waves in a predetermined direction. The wavelength width handled
by the wavelength of a radio wave is 0.01 to 1 m (see Reference 3). [Reference 3] Main
applications of each frequency band and characteristics of radio waves, [online], Ministry of
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25
Internal Affairs and Communications, [Search on February 28, 2014], Internet <http:
//www.tele.soumu.go .jp / j / adm / freq / search / myuse / summary /> However, in the case of
radio waves, since a specific wavelength is often used, the largest wavelength in the wavelength
width to be handled according to the specific wavelength It is desirable that the width is about
half the wavelength or more. It is desirable that the material of the high SN zone former 190 be
one that easily reflects radio waves. Therefore, a rigid and large-area rigid body may be used as
the high SN zone former 190. Also, for example, the high SN zone formation unit 190 may be
realized by a reinforcing bar, a building or the like.
[0101]
In the present embodiment, the parabola-shaped rigid body is the high SN zone former 190, but
the high SN zone former 190 may not be able to reflect sound waves. The point is that the high
SN zone is formed, and in the vicinity of the high SN zone, if the high SN zone former is present,
the area where the SN ratio is higher is formed compared with the case where the high SN zone
former is not present. Just do it. Thus, the high SN zone may be formed by methods other than
reflection. For example, a Fresnel lens (see Reference 4) or the like of sound may be used as the
high SN zone former 190. [Reference 4] "Fresnel lens of sound", [online], Nagoya City Science
Museum, [search on February 28, 2014], Internet <http://www.ncsm.city.nagoya.jp/cgi- bin /
visit / exhibition_guide / exhibit.cgi? id = S406 & key =% E3% 81% B5 & keyword =% E3% 83%
95% E3% 83% AC% E3% 83% 8D% E3% 83% AB% E3% 83% AC% E3% 83% B3% E3% 82% BA>
[0102]
In this case, the focal point of the Fresnel lens of sound corresponds to the high SN zone, the
vicinity of the focal point corresponds to the vicinity of the high SN zone, and the surface on
which the Fresnel lens of sound is disposed forms the high SN zone. It corresponds to the
formation surface. In the case of a sound Fresnel lens, since the wavelength width handled by the
sound wave is wide, the device scale tends to be large. In the case of using an electromagnetic
wave as a wave, a lens corresponding to each wavelength may be used. For example, when a light
wave is used as a wave, a normal lens may be used, and when a radio wave is used as a wave, a
radio wave lens may be used.
[0103]
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26
Note that “near a high SN zone” when a lens is used means the range “near a high SN zone”
in the direction perpendicular to a predetermined direction, inside the lens. Also, assuming that
the distance from the high SN zone formation surface J to the high SN zone F is JF, the range
from the high SN zone formation surface J to 2JF in the predetermined direction is “near the
high SN zone” in the predetermined direction See Figure 12).
[0104]
However, in this case as well, as in the case of using a concave high SN zone former capable of
reflecting waves, “near a high SN zone” can not be strictly defined, and the high SN zone
former 190 In some cases, this means a range in which the SN ratio is higher than when there is
no such case.
[0105]
In the present embodiment, although the directivity of the conversion unit is not mentioned, by
mixing and using electroacoustic transducers having various directivity, the correlation between
the transfer characteristics is reduced and decorrelation is achieved. It is also good.
For example, the directivity of the conversion unit is not limited, but when using a microphone as
the conversion unit, microphones having various directivity such as omnidirectionality,
unidirectionality, bidirectionality, hypercardioid are used in combination. Assuming that electroacoustic transducers having different directivity are placed at the same position, the transfer
characteristics with the same control point will be different. For example, when an
omnidirectional microphone and an omnidirectional microphone are arranged at the same
position, the transfer characteristic between the control point and the omnidirectional
microphone, and the control point and the omnidirectional microphone The transfer
characteristic between them is different. Therefore, under these conditions, the change in the
transfer characteristic due to the difference in directivity is used to further reduce the correlation
between the transfer characteristics, thereby achieving decorrelation. In other words,
decorrelation is achieved by setting the directivity of at least one of the plurality of microphones
to be different from the directivity of one other microphone.
[0106]
Second Embodiment A description will be made focusing on parts different from the first
embodiment.
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27
[0107]
In the present embodiment, an example of applying the present invention to a conversion
technique for converting a signal into a wave will be described.
The following techniques are mentioned as an example of the conversion technique which
converts a signal into a wave. There are (i) techniques for converting electrical signals to sound
waves, and (ii) techniques for converting electrical signals to electromagnetic waves. However,
the invention is not limited to this, and (iii) a technique for converting an optical signal into a
sound wave may be used. There is a speaker as a device which realizes (i). A device for realizing
(ii) is a transmitting antenna. Also, if there is hardware that can directly realize (iii), it may be
used.
[0108]
In particular, in the present embodiment, a case will be described in which sound waves are used
as waves, and a plurality of speakers (speaker arrays) for converting electrical signals into sound
waves are used as a plurality of conversion units instead of a microphone array consisting of a
plurality of microphones. .
[0109]
The present embodiment relates to a reproducing apparatus which physically modulates the
transfer characteristic based on diffusion sensing.
[0110]
[Signal Processing of Reproduction Device 30] It is considered to perform directivity control as
emphasized at the control point D using M (≧ 2) speakers.
[0111]
The functional configuration and processing flow of the playback device 30 according to the
second embodiment are shown in FIG. 13 and FIG.
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The reproduction apparatus 30 according to the second embodiment includes M speakers 311m, a frequency domain conversion unit 300, a filtering unit 330, a time domain conversion unit
340, a filter calculation unit 320, a transfer characteristic storage unit 310, and a high SN zone
formation. Vessel 390 is included.
m=1,2,…,Mであり、M≧2である。
[0112]
The signal source 200 outputs a sound source signal s (t).
In this embodiment, the sound source signal s (t) from the signal source 200 is assumed to be a
digital signal. However, when using an analog signal as a sound source signal, an AD conversion
unit that AD converts an analog signal to a digital signal s (t) may be provided.
[0113]
<Frequency domain converter 300> First, the frequency domain converter 300 receives the
digital signal s (t), stores N samples in a buffer, and outputs a digital signal s (τ) in frame units.
Next, the frequency domain conversion unit 300 converts the digital signal s (τ) of each frame
into a signal S (ω, τ) in the frequency domain and outputs (s31).
[0114]
<Transfer Characteristic Storage Unit 310 and Filter Calculation Unit 320> The functional
configurations of the transfer characteristic storage unit 310 and the filter calculation unit 320
are the same as in the first embodiment. For example, the filter calculation unit 320 takes out the
transfer characteristic A <→> (ω) from the transfer characteristic storage unit 310, calculates
the filter W <→> (ω) according to the method described in reference 5, and Output. For example,
a filter W <> →> (ω) used for signal processing to suppress an acoustic signal to a specific
position or direction is calculated. [Reference 5] Yoichi Haneda, Akira Kataoka, "Real Space
Performance of a Small Speaker Array Based on Multipoint Control Using Free Space Transfer
Function," Proceedings of the Acoustical Society of Japan, 2008, pp. 631-632
11-04-2019
29
[0115]
<Filtering unit 330> The filtering unit 330 receives the filter W <>> (ω) in advance from the
filter calculation unit 320, receives the frequency domain signal S (ω, τ), and for each frame τ,
each frequency ω ∈ Ω For the frequency domain signal S (ω, τ), apply the filter W <→> (ω)
(see the following equation, s32) to output signal Z <→> (ω, τ) = [Z 1 (ω) , τ),..., ZM (ω, τ)].
[0116]
[0117]
For example, the filtering unit 330 may have different reproduction characteristics of acoustic
signals emitted from the M speakers 311-m at least at a plurality of positions in space.
“Differentiating reproduction characteristics” means, for example, local reproduction of an
acoustic signal at a specific position so that the acoustic signal is not reproduced at other
positions as much as possible, and conversely, the acoustic signal is not reproduced at a specific
position. It means that the sound signal is reproduced only at other positions.
[0118]
<Time domain conversion unit 340> The time domain conversion unit 340 is a reproduction
signal Z <→> (ω, τ) = [Z 1 (ω, τ),. , τ)] to the time domain (s33) to obtain a frame unit time
domain signal z <→> (τ) = [z 1 (τ), ..., z M (τ)] of the τ frame Further, the obtained frame unit
time domain signal z <→> (τ) = [z 1 (τ),..., Z M (τ)] is linked in the order of the index of the
frame number, and the time domain signal z <→> (t) = [z 1 (t),..., Z M (t)] is output.
The method of converting the frequency domain signal into the time domain signal is an inverse
transform corresponding to the conversion method used in the process of s31, and is, for
example, high-speed discrete inverse Fourier transform.
[0119]
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30
<Speaker 311-m and High SN Zone-Former 390> The M-channel time-domain signals z 1 (t),..., Z
M (t) are selected from among the M speakers 311 forming the speaker array as channels. It
reproduces | regenerates with a corresponding speaker (s34).
[0120]
The high SN zone former 390 has the same configuration as the high SN zone former 190 of the
first embodiment.
Note that the positional relationship of the M speakers with respect to the high SN zone former
390 corresponds to the high SN zone former 190 and the M microphones 211-m of the first
embodiment, the high SN zone former 390 and the M speakers according to the first
embodiment. It may be replaced with 311-m respectively. That is, M speakers may be arranged
such that the determinant det (R) of the spatial correlation matrix R is maximized. M speakers are
placed near the high SN zone (focal point) in order to increase the SN ratio. Also, M speakers are
placed at different positions so that the inter-channel correlation is low. In other words, the M
speakers may be arranged so that the correlation between the sound waves converted into
electric signals by the M speakers is low.
[0121]
<Effects> With such a configuration, it is possible to reduce the correlation between channels and
further shorten the impulse response length and the filter length, and to reproduce the sound
wave stably in various directions simultaneously with high spatial resolution. Becomes possible.
For example, arbitrary directional control can be performed over a wide band by performing
appropriate signal processing using a filter using a transfer characteristic prepared in advance. In
the present embodiment, the filter W <→> (ω) is calculated in advance, but the filter calculation
unit 350 may be configured after the reproduction position and the arrangement of the
microphones are determined according to the calculation processing capability of the
reproduction device 30 or the like. The filter W <→> (ω) may be calculated for each frequency.
[0122]
<Modifications> As in the first embodiment, sound waves are used as waves, but radio waves or
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31
light waves may be used, or electromagnetic waves in other bands may be used. In that case, a
transmitting antenna, a light emitting element, or the like can be used instead of the speaker. The
point is that a plurality of conversion units capable of converting the signal into waves of the
same type may be used. The converter may be called a transmitter in the sense that waves can be
transmitted. The receiver and the transmitter described in the modification of the first
embodiment may be collectively referred to as a transmitter / receiver. Also, the conversion unit
may be called a wave source output unit in the sense that it becomes a wave source and outputs
a wave. In addition, you may call it a wave source input-output part together with the wave
source input part demonstrated by the modification of 1st embodiment.
[0123]
The same modification as that of the first embodiment is possible by replacing the microphone
with a speaker.
[0124]
Third Embodiment A description will be made focusing on parts different from the first
embodiment.
[0125]
<Point of Third Embodiment> Similar to the first embodiment, in this embodiment, the idea of
reducing the inter-channel correlation in the zoom-up microphones of Non-Patent Documents 2
and 3 is inherited in this embodiment, and the impulse response length is further shortened.
While increasing the signal-to-noise ratio at the time of sound reception.
[0126]
In the first embodiment, M high microphones 211-m are provided for one high SN zone former
190.
On the other hand, in the present embodiment, N high SN zone formers 190-n are included, and
M n microphones 211-m n are provided for each high SN zone former 190-n.
Note that N is an integer of 2 or more, n = 1, 2,..., N, and M n is an integer of 1 or more
corresponding to n (which changes according to n), mn = 1,. .
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Then, at least one microphone 211-m n of (Σ n = 1 <N> M n) microphones 211-m n is a high SN
zone formation unit 190-n corresponding to the microphone 211-m n By arranging the position
in a position other than the high SN zone formed, the determinant det (R) is maximized.
[0127]
In the present embodiment, in order to increase the SN ratio at the time of sound reception, high
SN zones are respectively formed using N high SN zone forming devices, and a plurality of
microphones are arranged in the vicinity of each high SN zone. At this time, in order to reduce
inter-channel correlation, at least one microphone 211-m n is a position other than the high SN
zone formed by the n-th high SN zone former 190-n corresponding to the microphone 211-m n
Place on
[0128]
[Requirement Condition] (1) Including N high SN zone formers forming N high SN zones, and
including N high SN zone formers 190-n. Each high SN zone former 190-n has the same
configuration as the high SN zone former 190 of the first embodiment.
[0129]
(2)
Including M n microphones located near the high SN zone formed by each high SN zone former
190-n. Furthermore, at least one microphone 211-m n of (Σ n = 1 <N> M n) microphones 211-m
n corresponds to the high SN zone former 190-n corresponding to the microphone 211-m n
Place in a position other than the high SN zone formed by In order to arrange at least one
microphone 211-m n for each high SN zone former 190-n, the required minimum number of
microphones 211-m n is N.
[0130]
(3)
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Including a filtering unit (Σ n = 1 <N> M n) A filtering unit 160 capable of performing
independent filtering on each of the microphones. The processing content is the same as that of
the filtering unit 160 of the first embodiment except that the number of input signals is different.
[0131]
<Outline of Third Embodiment> In the present embodiment, the characteristics in the vicinity of
the high SN zone described in the first embodiment are used, and Mn in the vicinity of the high
SN zone formed by each high SN zone formation unit 190-n. Arrange the microphones to
increase the signal-to-noise ratio.
[0132]
In addition, at least one microphone 211-m n of (Σ n = 1 <N> M n) microphones 211-m n is a
high SN zone former 190-n corresponding to the microphone 211-m n The inter-channel
correlation is reduced by disposing at a position other than the high SN zone formed by
[0133]
In particular, by arranging the positional relationship of the microphone 211-mn_A with respect
to the high SN zone former 190-n A and the positional relationship of the microphone 211-mn_B
with respect to the high SN zone former 190-n B different from each other. Inter-channel
correlation can be further reduced.
However, even if the positional relationship of all the microphones 211-m n with the N high SN
zone formers 190-n is the same, the microphones 211-m n are located at positions other than
the high SN zone F as shown in FIG. It should just be arrange | positioned.
The high SN zone former 190-n having a parabola shape or the like has a shape in which the
sound wave gathers in the high SN zone, so if the microphone 211-mn is arranged at a position
other than the high SN zone As compared with the case where all the microphones are arranged
in the high SN zone as in Document 1, the correlation between the sound wave picked up by the
microphone 211-mn_A and the sound wave picked up by the microphone 211-mn_B becomes
lower, Even with such a configuration, the determinant det (R) can be maximized.
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[0134]
<Sound Collection Device 50 According to Third Embodiment> [Signal Processing of Sound
Collection Device 50] The functional configuration of the sound collection device 50 according to
the third embodiment is shown in FIG. The processing flow is the same as that of the sound
collection device 10 according to the first embodiment. The sound collection device 50 according
to the third embodiment includes an AD conversion unit 120, a frequency domain conversion
unit 130, a filtering unit 160, a time domain conversion unit 170, a filter calculation unit 150, a
transfer characteristic storage unit 140, and N high SN zones. A former 190-n includes (Σ n = 1
<N> M n) microphones 211-m n.
[0135]
The configurations of the AD conversion unit 120, the frequency domain conversion unit 130,
the filtering unit 160, the time domain conversion unit 170, the filter calculation unit 150, and
the transfer characteristic storage unit 140 are the same as in the first embodiment.
[0136]
However, instead of M microphones 211-m, (Σ n = 1 <N> M n) microphones 211-m n are picked
up and picked up (Σ n = 1 <N> Mn Each analog signal or the value corresponding to the analog
signal is used for each processing.
[0137]
The <high SN zone former 190-n and the microphones 211-mn> N high SN zone formers 190-n
have the same configuration as the high SN zone former 190 of the first embodiment.
[0138]
The (Σ n = 1 <N> M n) microphones 211-m n have the same configuration as the microphones
211-m of the first embodiment.
[0139]
M n microphones 211-m n are provided for one high SN zone former 190-n.
[0140]
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<Position of microphone 211-mn with respect to high SN zone former 190-n> (Σ n = 1 <N> Mn)
pieces so that the determinant det (R) of the spatial correlation matrix R is maximized The
microphones 211-mn may be arranged.
As described above, the high SN zone formation device corresponding to at least one microphone
211-m n of (Σ n = 1 <N> M n) microphones 211-m n corresponding to the microphone 211-m n
By arranging at a position other than the high SN zone (for example, focal point) formed by 190n, the correlation between channels is reduced, and the determinant det (R) is maximized.
In particular, the positional relationship of the microphone 211 -mn_A with respect to the high
SN zone former 190-n A and the positional relationship of the microphone 211 -mn = B with
respect to the high SN zone former 190-n B are different. Inter-channel correlation can be further
reduced.
However, subscripts n_A and n_B respectively represent n A and n B, and let n A and n B be
specific values among 1, 2, ..., N, and n A n n B.
[0141]
In other words, the plurality of microphones may be arranged such that the correlation between
the sound waves converted into the electric signal by the plurality of microphones is low.
As a whole, it is desirable to arrange a plurality of microphones so that the correlation is low, but
at least one (? N = 1 <N> M n) microphones 211-m n so that one correlation is low. You can get
the effect by placing.
In other words, among the (n n = 1 <N> M n) microphones, the combination of correlations
between sound waves converted by any two microphones can be considered as PC 2 (but P = N n
= 1 <N> M n) Of the correlation combinations PC 2, at least one of the 2 combinations is low (Σ
n = 1 <N> M n) microphones 211-m n It should be arranged.
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[0142]
FIG. 17 and FIG. 18 each show an arrangement example of the microphones 211-mn with
respect to the high SN zone former 190-n.
[0143]
In this embodiment, the microphones 211-m n are supported by the support portion 191-n
having a shape that does not easily block the waves arriving to the high SN zone former 190-n.
The support portion 191-n has the same configuration as the support portion 191 of the first
embodiment.
[0144]
In FIG. 17, the support portion 191-n is a structure including a surface located near the high SN
zone formed by the high SN zone former 190-n, and holds the microphone 211-m n on that
surface. A plurality of pores are formed.
[0145]
In FIG. 18, the support portion 191-n is a rod-like structure that couples the high SN zone former
190-n and the microphone 211-m n.
FIG. 18 shows an example in the case of N = 3, M 1 = 3, M 2 = 3 and M 3 = 1.
[0146]
In any of the examples, at least one microphone 211-mn of (Σ n = 1 <N> Mn) microphones 211mn is formed into a high SN zone corresponding to the microphone 211-mn. It arrange |
positions in positions other than the high SN zone (for example, focus) which unit 190-n forms.
Further, the positional relationship of the microphone 211 -mn_A with respect to the high SN
zone former 190-n A and the positional relationship of the microphone 211 -mn n B with respect
to the high SN zone former 190-n B are arranged to be different. With such a configuration, since
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the positional relationship is different, the correlation between the sound wave picked up by the
microphone 211-mn_A and the sound wave picked up by the microphone 211-mn_B becomes
low. As described above, since the microphones 211-m n are disposed near the high SN zone of
the corresponding high SN zone former 190-n, the SN ratio becomes high. Thus, with such a
configuration, the determinant det (R) can be maximized.
[0147]
<Effect> According to such a configuration, the same effect as that of the first embodiment can
be obtained. The point of the present embodiment is that at least one microphone 211-mn
among ((n = 1 <N> Mn) microphones 211-mn corresponds to the microphone 211-mn. n is
located at a position other than the high SN zone formed by the high SN zone former, and
further, the positional relationship of the microphone 211 -mn_A with respect to the high SN
zone former 190-n A and the high SN zone former The microphones 211-m n ̶ A and the
microphones 211-m n ̶ B are arranged such that the positional relationship of the microphones
211-m n ̶ B with respect to 190-n B is different. If this point is included, the first embodiment It
may be combined with the second embodiment. For example, FIG. 17 and FIG. 18 show a
combination with the first embodiment, for example, in FIG. 18 at different positions near high
SN zones formed by high SN zone formers 190-1 and 190-2, respectively. The microphones 2111 to 211-3 1 and the microphones 211-1 to 211-3 2 are disposed, respectively. Furthermore, the
microphones 211-1 to 211-31, the microphones 211-1 to 211-32, and the microphones 211 to
13 respectively correspond to the high SN zone formers 190-1, 190-2 and 190-3. Are disposed
at positions other than the high SN zone formed by Further, the positional relationship of the
microphones 211-1 to 211-3 1 with respect to the high SN zone forming unit 190-1 and the
positional relationship of the microphones 211-12 to 211-3 2 with respect to the high SN zone
forming unit 190-2. The positional relationship of the microphones 211-13 with respect to the
high SN zone former 190-3 is arranged to be different. The same modification as the first
embodiment and the second embodiment can be applied.
[0148]
<Other Modifications> The present invention is not limited to the above embodiment and
modifications. For example, the various processes described above may be performed not only in
chronological order according to the description, but also in parallel or individually depending on
the processing capability of the apparatus that executes the process or the necessity. In addition,
changes can be made as appropriate without departing from the spirit of the present invention.
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[0149]
<Program and Recording Medium> In addition, various processing functions in each device
described in the above embodiment and modification may be realized by a computer. In that
case, the processing content of the function that each device should have is described by a
program. By executing this program on a computer, various processing functions in each of the
above-described devices are realized on the computer.
[0150]
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.
[0151]
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, the 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.
[0152]
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 unit. Then, at the time of execution of the process, the computer reads the program
stored in its storage unit and executes the process according to the read program. In another
embodiment of the program, the computer may read the program directly from the portable
recording medium and execute processing in accordance with the program. Furthermore, each
time a program is transferred from this server computer to this computer, processing according
to the received program may be executed sequentially. In addition, a configuration in which the
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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 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).
[0153]
In addition, although each device is configured by executing a predetermined program on a
computer, at least a part of the processing content may be realized as hardware.
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