JP2001313992A - Sound pickup device and sound pickup method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a calculated amount when calculating power or correlation about a sampling time difference in the case where the sampling time difference is large. SOLUTION: The power of a sound pickup signal obtained by correcting a delay time with a propagating time by using a propagating time recording means to record a plurality of correspondence relations between the propagating time of an acoustic wave from a representative position to each microphone and the range of the propagating time, is calculated as first power (S1). The representative position corresponding to the propagating time making the first power maximum is selected (S2), and then the power of the sound pickup signal obtained by correcting the delay time about each propagating time belonging to the range of the propagating time corresponding to the representative position is calculated as second power (S4). The propagating time making the second power maximum is determined (S5), and then the sound pickup signal obtained by correcting the delay time about the determined propagating time (S6) is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a means for satisfactorily recording a target sound using a microphone array composed of a plurality of microphones.

[0002]

2. Description of the Related Art In recent years, with the advancement of multimedia technology, it has become possible to conduct a teleconference such as a video conference using a microphone and a speaker in a voice call mode.
In such a case, there is a need for a sound collecting device capable of making a natural call without being aware of the microphones and installing only a target sound such as voice without installing microphones for the number of speakers on the desk of the communication conference. I have.

[0003] As an example of such a sound pickup device, there is a sound pickup device in which a plurality of microphones (microphone arrays) are installed and their outputs are subjected to signal processing to extract a target sound. Signal processing methods for suppressing noise and extracting a target sound using such a microphone array include a delay-and-sum method and an AM method.
Many are known, such as NOR (for example, Oga, Yamazaki, and Kaneda, "Acoustic System and Digital Processing", IEICE, 1995, pp.173-197). Extract sound.

FIG. 8 is a diagram for explaining the principle of target sound extraction by the delay-and-sum method. 8, 1 is the sound pickup unit (microphone _{array), 2 1, 2 2,} ..., 2 M microphones
(M is the number of microphones), 3 ₁ , 3 ₂ , ..., 3 _M is a delay unit, 4 is an adder, 5 is an output signal, 6 is a noise suppression unit, d is a microphone interval, and s (t) is sound pickup The sound wave arriving at the unit 1 (t represents time), and θ is the angle of arrival of the sound wave s (t) arriving at the sound collection unit 1.

The microphones 2 ₁ , 2 ₂ ,..., 2 _M shown in FIG. 8 are arranged in a straight line at equal intervals d, and the sound wave s (t) arrives at a microphone at an angle θ from a distance. And
The distance the sound wave reaching the microphone 2 ₁ propagates before reaching the microphone 2 ₂ is expressed by dsinθ from a microphone spacing d between the arrival month theta (Fig. 8). Similarly, the distance that the light propagates to reach the i-th microphone 2 _i (i = 2, 3,..., M) is represented by (i−1) dsin θ. Accordingly, the microphone _{2 i (i = 2,3, ...} , M) is a delay time tau _i to reach, when the reference microphone 2 _1, by dividing the propagation distance at the speed of sound c, the following equation (1 )
Is represented by

[0006]

(Equation 1)

Here, each microphone 2 _i (i = 1, 2,
, M), the output signal from x) is represented by x _i (t).
Since (t) is delayed by τ _i , the following equation (2) is obtained.

[0008]

(Equation 2)

Here, the following describes that, when the delay amount D _i of the delay unit 3 _i (i = 1, 2,... M) is appropriately set, only the sound wave arriving from the θ direction can be enhanced and output to the output signal 5. Show.

The delay amount D _{i of the} delay unit 3 _i (i = 1, 2,..., M)
Is set as in the following equation (3).

[0011]

(Equation 3)

D ₀ is a fixed delay amount added to prevent a decrease in accuracy in realizing delay characteristics with a digital filter when the value of τ _i is too small.

At this time, the output of the delay unit 3 _i (i = 1, 2,..., M) is obtained by adding the delay D _i of the equation (3) to the signal of the equation (2). )become that way.

[0014]

(Equation 4)

That is, s (t) is the same signal delayed by D ₀ irrespective of the microphone number i.

If the signals are added by the adder 4 after the phases are aligned in this manner, the sound waves arriving from the θ direction are emphasized by the added amount. On the other hand, sound waves and theta directions coming from another theta _N direction, since it is sound receiving with different delay times tau _N and tau _i, the phase is not aligned in the delay amount of a compound of formula (3), by the adder 4 Addition of the signals does not add emphasis.

As described above, in the delay-and-sum method, the sound wave coming from the target direction θ is emphasized, and the noise coming from the other direction θ _N is relatively suppressed.

At this time, if the output signal of the microphone array is monitored by scanning the target direction θ and monitoring the output signal of the microphone array, the output signal becomes large when θ is directed to the target speaker. Can be. Then, the target sound is increased by aligning and adding the phases according to Equation (4) so as to emphasize the sound wave from the direction θ of the target speaker, that is, by directing the directivity of the microphone array in the direction of θ. Sound can be collected at the SN ratio.

Here, for convenience of explanation, a plurality of microphones are described as being arranged on a straight line at equal intervals d. However, the microphones may be arranged at irregular intervals, and the arrangement shape may be two-dimensional. May be arranged in three dimensions.

Further, when located relatively close distance point sound sound source S is in the array as shown in Figure 9, by using the spherical wave nature of the sound source S, the delay unit 3 _1, 3 ₂ , ... 3 _M
Gain 7 _1, 7 ₂ to the subsequent, ..., a 7 _M provided, to provide appropriate load this gain is important in improving the sound collection SN ratio. As a method of applying a load, there is a method of applying the following expressions (5), (6), (7) (Nomura, Kaneda, Kojima `` Near-field microphone array '', Journal of the Acoustical Society of Japan 53 Volume 2 (19
97), pp. 110-116).

[0021]

(Equation 5)

[0022] Here _{r 1, r 2, ...,} r M ₁ 2 each microphone from the sound source S, _{2 2,} ..., a distance of up to 2 _M, r _c is the room of critical distance, that is, the direct sound power of the sound source and the distance where the reverberant sound power is equal, the chamber volume V [m ^2], with respect to the chamber of the reverberation time T [sec] is expressed by _{r c = √ (0.0032V / T} ) (H.Ku
ttruff, "Room Acoustics (Third Edition)", Elsevier
Applied Science, pp. 100-132 (1991)). At this time, the microphone array has the highest sensitivity with respect to the "point" of the position of the sound source S, so that a "focus" of the sensitivity is formed. At this time, the delay units 3 ₁ , 3 ₂ ,... With respect to the distance r _i (i = 1, 2,..., M) to each microphone.
..., 3 delay D of _{M 0 -r i / c (c} : sound velocity) and the above-mentioned gain g ₀
If the focus of the sensitivity is scanned by changing (vector), that is, a (vector), and the array output is monitored, the array output becomes large when the focus of the sensitivity is directed to the point where the target speaker exists. Thus, the position of the target speaker can be found.

In this way, by finding the target speaker's existence area as the direction or position and directing the array directivity to the existence area, the target sound can be collected with a high sound collection SN ratio.

[0024] Here, the presence region of the sound source delayer 3 _1, 3 _2, ..., deviates from the delay D ₀ -r _i / c which is set to 3 _M, to be out of focus in the sensitivity of the array Become
Sound pickup performance deteriorates. To prevent this, refocus when the area where the sound source exists is out of focus.
Correct the delay D ₀ -r _i / c. The correction is to estimate the delay r _i / c corresponding to the distance between the sound source and the i-th microphone, may be corrected delay D ₀ -r _i / c. This estimation includes, for example, a method of calculating the correlation between the outputs of the microphones and estimating the delay r _i / c as the time at which the correlation is maximum (for example, HF Si1verman et al, “A two-stage
algorithm for determining ta1ker location from li
near microphone array data ", Comuputer Speech and
Language (1992) 6, pp. 129-152). The correlation C _ij (m) at time m between the output x _i (n) (n: discrete time) of the i-th microphone and the output x _j (n) of the j-th microphone is calculated by the following equation (8). Here, J is the length of the section for calculating the correlation.

[0025]

(Equation 6)

M which maximizes C _ij (m) is a relative delay time of the j-th microphone output with respect to the i-th microphone output. To find m at which the correlation of equation (8) is maximized, basically, discrete time m
Is incremented by 1 to find an m that maximizes C _ij (m).

[Problems to be Solved by the Invention] A sufficiently large time or a time difference range is set in advance assuming that the distance from the sound source to the microphones or the distance between the microphones, that is, the delay time or the delay time difference is large. There is a need. That is, assuming that the distance or the distance difference for calculating the correlation or power for determining the delay time or the delay time difference, that is, when the sample time difference m is large, it is necessary to set a sufficiently large sample time difference range in advance. is there. If the power or correlation is calculated for each sample time difference, the amount of calculation becomes enormous. When processing in real time, it is necessary to reduce this calculation amount.

[0028]

In order to solve the above-mentioned problems, the present invention has the following means.

According to a first mode of the present invention (claim 1), sound signals recorded by a plurality of microphones are delayed by independent delay times, and the respective delayed signals are added to obtain a sound pickup signal. Implemented as a method. In the method, a propagation time recording unit that records a plurality of correspondences between a representative position and a propagation time of a sound wave from the representative position to each of the microphones and the range of the propagation time is used, and the delay time is corrected by the propagation time. Is calculated as the first power (S1), a representative position corresponding to the propagation time that maximizes the first power is selected (S2), and the representative position corresponding to the representative position is selected. The power of the picked-up signal obtained by correcting the delay time for each propagation time belonging to the range of
(S4), determine the propagation time that maximizes the second power (S5), correct the delay time for the determined propagation time (S6), and output the obtained sound pickup signal. I do.

A second embodiment of the present invention (claim 2)
Is realized as a sound collecting method in which sound signals recorded by a plurality of microphones are respectively delayed by independent delay times, and the respective delayed signals are added to obtain a sound collecting signal. In the sound collection method, using a propagation time recording unit that records a plurality of correspondences between a representative position, a propagation time of a sound wave from the sound source position to each of the microphones, and a range of a propagation time difference between the microphones, The power of the sound pickup signal obtained by correcting the delay time with the propagation time is calculated (S1), and a representative position corresponding to the propagation time that maximizes the power is selected (S1).
2) calculating a cross-correlation between the microphones for each propagation time difference belonging to the range of the propagation time difference corresponding to the representative position (S4), and determining a propagation time difference that maximizes the cross-correlation (S5); The delay time is corrected for the obtained propagation time difference (S6), and a sound pickup signal is output.

A third aspect of the present invention (claim 3)
Is realized as a sound collecting device that delays audio signals recorded by a plurality of microphones with independent delay times and adds the respective delayed signals to obtain a sound collecting signal. The apparatus includes a plurality of microphones, is connected to a microphone array (22) that converts sound detected by each of the plurality of microphones and outputs a plurality of independent signals, and is connected to an output of the microphone array. A delay-and-sum array device that adds an independent delay amount to each of a plurality of independent signals, adds the delay amount, and adds the output signals to generate a pickup signal and outputs the pickup signal. (6)
And a storage unit (23) storing a plurality of correspondences between a representative position, a propagation time of a sound wave from the representative position to each of the microphones, and the range of the propagation time, and a delay time corrected by the propagation time. A sound source that calculates the power of the sound pickup signal from the delay-and-sum array device as a first power and selects a representative position corresponding to a propagation time that maximizes the first power by referring to the storage unit; A position determining unit (25) for obtaining a range of the propagation time corresponding to the representative position from the storage unit, and correcting the delay time for each of the propagation times belonging to the range to obtain a second power of the collected sound signal.
And a delay time calculating unit (24) that determines a propagation time that maximizes the second power. The delay-and-sum array device includes a delay time calculating unit that calculates the propagation time determined by the delay time calculating unit. Each of the independent delay amounts is corrected according to time.

A fourth embodiment of the present invention (Claim 4)
Is realized as a sound collecting device that delays audio signals recorded by a plurality of microphones with independent delay times and adds the respective delayed signals to obtain a sound collecting signal. The apparatus includes a plurality of microphones, is connected to a microphone array (22) that converts sound detected by each of the plurality of microphones and outputs a plurality of independent signals, and is connected to an output of the microphone array. A delay-and-sum array device that adds an independent delay amount to each of a plurality of independent signals, adds the delay amount, and adds the output signals to generate a pickup signal and outputs the pickup signal. (6)
A storage unit (2) for recording a plurality of correspondences between a representative position, a propagation time of a sound wave from the sound source position to each of the microphones, and a range of a propagation time difference between the microphones.
3) calculating the power of the picked-up signal obtained by correcting the delay time with the propagation time, connected to the output of the delay-and-sum array device, and determining the representative position corresponding to the propagation time that maximizes the power. Calculating a cross-correlation between the microphones for each of the propagation time differences belonging to the range of the propagation time difference corresponding to the representative position, and determining a propagation time difference that maximizes the cross-correlation; A delay time calculating unit (24), wherein the delay-and-sum array device corrects each of the independent delay amounts according to the propagation time difference determined by the delay time calculating unit.
It is characterized by the following.

A fifth aspect of the present invention (claim 5)
The storage unit (23) in which a plurality of representative positions, a propagation time of a sound wave from each of the plurality of representative positions to each of the plurality of microphones, and a range of the propagation time are stored in association with each other. ), A plurality of microphones, a microphone array (22) configured to convert sound detected by each of the plurality of microphones and output a plurality of independent signals, and a microphone array (22) connected to an output of the microphone array. A delay-and-sum array device that generates a collected sound signal by adding an independent delay amount to each of the independent signals, adds the delayed amount of the output signal, and outputs the collected sound signal ( 6), a representative position corresponding to the position of the sound source connected to the output of the picked-up signal of the delay-and-sum array device, and by determining the output, the representative position stored in the storage unit. Sound source position determination unit that selects from (2
5) and referring to the range of the propagation time corresponding to the representative position stored in the storage unit based on the representative position selected by the sound source position determination unit, and based on the range of the propagation time. A delay time calculation unit (24) for calculating a delay amount added to each of the plurality of independent signals in the delay-and-sum array device, wherein the delay time calculation unit includes a range of a propagation time corresponding to the representative position. At
The delay amount is estimated by calculating the correlation between the outputs of the microphones, and the delay amount that maximizes the output of the collected signal is determined from the estimated delay amount. The delay amount of each of the plurality of delay elements is corrected according to the delay amount determined by the calculation unit.

[Operation] In the first and third aspects of the invention, the power is maximized from the correspondence between the representative position, the propagation time of the sound wave from the representative position to the name microphone, and the range of the propagation time. The representative position or the range of the propagation time corresponding to the propagation time is determined. Each small area is determined in advance so as to fill the entire space without overlapping each other. Here, the “propagation time” refers to the time required for a sound wave from a sound source to reach each microphone. The range of each propagation time is determined by the maximum propagation time from the position farthest to the microphone and the minimum propagation time to the nearest position in a small area (for example, a square area of several tens of cm square) including the representative position. Therefore, it is only necessary to specify the propagation time from the range of the determined propagation time, so that the calculation amount can be reduced.

Similarly, in the inventions of the second and fourth embodiments, since the range of the propagation time difference is selected in advance, the amount of calculation for determining the propagation time at which the correlation becomes maximum can be reduced.

Also, in the fifth aspect of the invention,
Since the range in which the correlation calculation needs to be performed is limited to the range of the propagation time difference corresponding to the specified representative position, the amount of calculation for determining the propagation time can be reduced.

[0037]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart schematically showing the steps of the sound collection method according to the present invention. FIG. 2 is a flowchart showing the representative position, propagation time, and its range stored in the storage unit. FIG. 3 is a diagram illustrating an example of a correspondence relationship, and FIG. 3 is a conceptual diagram illustrating a relationship between a representative position, a propagation time, and a range thereof.

In the sound collection method according to the present invention, FIG.
As shown in (1), a plurality of representative positions P (represented by "X" marks in the figure) are previously set at arbitrary positions. For example, the representative position is assumed to be M number set, the representative position _{P 1, P 2, P 3} , ..., a P _M. In FIG. 3, the representative positions are arranged in a matrix. However, the present invention is not limited to this. The representative positions can be set according to an arbitrary arrangement method such as a concentric shape or a parabolic shape.

A small area S as shown in FIG. 3 is defined for each representative position. In the drawing, for convenience, the small area S is a representative position P _l (“l” is any natural number from 1 to N)
Are displayed, but similar small areas S are set for all other representative positions. The small region is a region having a corresponding representative position at its center, and is, for example, a square region having a side of several tens cm.

The propagation distance between one representative position P ₁ and one microphone 2 _k (assuming that N microphones are arranged, and “k” is any natural number from 1 to N) r _lk is determined. Similarly, the surrogate table position P _l and the other microphones 2 _{1, 2} 2, ..., propagation distance also _{2 M r l1, r l2,} ..., r lN is determined. That is,
For each of the M representative positions, there is a propagation distance equal to the number N of microphones.

The maximum propagation distance r _lkmax between one representative position P _l and one microphone 2 _k ,
The minimum propagation distance r _lkmin is determined. Maximum propagation distance r _lkmax
And refers to the distance between the farthest positions and the microphone to the microphone 2 _k in a small area S corresponding to the representative position P _l, and the minimum propagation distance r _Lkmin, small corresponding to the representative position P _l It refers to the distance between the closest position and the microphone to the microphone 2 _k in the area S. Moreover, surrogate table position P _l and the other microphones 2 _{1, 2} 2, ..., maximum propagation distance r _1Kmax also _{2 M, r 2kmax, ...,} r Mkmax and minimum propagation distance _{r 1 kmin, r 2kmin, ...} , r _Mkmin is determined. That is, for each of the M representative positions, there is a maximum propagation distance and a minimum propagation distance equal to the number N of microphones.

The values obtained by dividing the above "propagation distance", "maximum propagation distance", and "minimum propagation distance" by the sound velocity c are respectively a propagation time t _lk , a maximum propagation time t _lkmax , and a minimum propagation time t _{l kmin.} And Also, a range determined by the maximum propagation time for a certain representative position and the minimum propagation time to the nearest position is referred to as a “propagation time range”.

FIG. 2 shows an example of a storage configuration for storing the above “propagation time”, “maximum propagation time”, and “minimum propagation time” in association with “representative position”. The present invention is not limited to such a configuration example, and is configured such that “propagation time”, “maximum propagation time”, and “minimum propagation time” are stored in a storage unit described later in association with “representative position”.

The steps of the sound collection method according to the present invention shown in FIG. 1 will be described with reference to FIGS.

First, for each representative position, the output power of the sound pickup signal is determined (FIG. 1, S1). The power of the picked-up signal is calculated by, for example, the above-mentioned equations (5), (6), (7)
Is calculated using

If each power is obtained, one representative position where the power is maximum can be determined. A representative position where the power is maximum is selected (S2).

If one representative position is determined, the corresponding propagation time or range of the propagation time can be determined from the storage array as shown in FIG. 3 (S3).

When the propagation time or the range of the propagation time is determined, the power can be calculated by using these time values discretely, or the correlation can be calculated by using the above-mentioned equation (8). (S4).

The maximum power or correlation obtained in this manner is determined (S5).

The time value (corresponding to the discrete time m in equation (8)) that maximizes the power and correlation is determined by the above processing, and the time value is used for each channel (output of each microphone). The added delay can be estimated, and each delay time (corresponding to the delay amount of the delay element in FIGS. 1 and 2) is corrected using the estimated delay (S6).

By the correction, in the sound pickup device shown in FIG. 1 or FIG. 2, the delay amount D _i of the delay unit 3 _i (i = 1, 2,... M) is appropriately set. Therefore, only the sound wave arriving from the θ direction can be emphasized and output as the output signal 5.

[0053] That is, the delay unit _{3 i (i = 1,2, ...} , M) the delay amount D _i of being set as the equation (3). D
₀ is a fixed delay amount added to prevent a decrease in accuracy when realizing delay characteristics with a digital filter when the value of τ _i is too small.

At this time, the output of the delay unit 3 _i (i = 1, 2,..., M) is the signal of the above equation (2) with the delay D _i of the above equation (3). It becomes like (4). That is, regardless of the number i of the microphone, s (t) is the same signal delayed by D _0. If the signals are added by the adder 4 after the phases are aligned in this way, the sound waves coming from the θ direction are emphasized by the added amount. On the other hand, θ
Sound waves arriving from another theta _N direction to the direction to be received sound with different delay times tau _N and tau _i, the phase is not aligned in the delay amount of a compound of formula (3), plus the signal by the adder 4 There is no emphasis when combined. In this manner, sound waves arriving from the target direction θ can be emphasized, and noise arriving from other directions θ _N can be relatively suppressed. At this time,
If the output signal of the microphone array is monitored by scanning the target direction θ and the output signal of the microphone array is monitored, the direction of the target speaker can be searched because the output signal increases when θ is directed to the target speaker. Then, the target sound is increased by aligning and adding the phases according to Equation (4) so as to emphasize the sound wave from the direction θ of the target speaker, that is, by directing the directivity of the microphone array in the direction of θ. Sound can be collected at the SN ratio.

Next, an embodiment of the sound collecting apparatus according to the present invention will be described.

FIG. 4 shows a first example of the configuration of a sound collection device according to the present invention. In this figure, a sound collection device (microphone array processing device) 21 includes a microphone array 22 composed of a plurality of microphones, a delay-and-sum array device 6 connected to an output of the microphone array 22, and a microphone array 22. A storage unit 23 that stores a distance delay time corresponding to a distance from the focus of the sensitivity set in advance to each microphone constituting the microphone array 22,
Sound source position determination for calculating the power for each focus from the output of the delay-and-sum array device 6 for the focus of a plurality of sensitivities set in advance of the microphone array 22 and determining the sound source position from the focus information of the maximum and second largest power Part 25
This embodiment comprises a delay time calculation unit 24 that calculates a propagation delay time when a sound wave reaches a microphone from a sound source using the distance delay time of the storage unit 23.

With these configurations, a sound collection method as shown in FIG. 1 can be executed.

FIG. 5 shows a second example of the configuration of the sound pickup device according to the present invention. This configuration is basically the same as the configuration of the sound pickup device shown in FIG. 3A, and the delay time calculating unit 24 uses the information of the distance delay time in the storage unit 23 to calculate the distance delay time. This is an embodiment comprising an extraction unit 26 for extracting the output from the microphone so as to remove it, and a correlation calculation unit 27 for calculating the correlation between the outputs of the microphone using the signal extracted by the extraction unit.

FIG. 6 shows a third configuration example of the sound pickup device according to the present invention. This configuration is basically the same as the configuration of the sound collection device shown in FIG. 5, except that it is connected between the extraction unit and the correlation calculation unit, and performs whitening processing on the output from the extraction unit. The difference is that a whitening unit 31 for sending the whitened output to the correlation calculation unit is provided. The whitening unit 31 flattens the frequency characteristics of the output of each microphone constituting the microphone array 22. The whitening section 31 performs a whitening process. A typical method of the whitening process is as follows. First, the microphone output x (t) in the time domain is converted to the frequency domain. For the microphone output X (k) expressed in the frequency domain, the frequency characteristic is flattened by dividing | X (k) + δ | to convert it to the time domain. However, δ is a very small amount for preventing the denominator from becoming zero. If the whitening process is not performed, the peak of the time characteristic of the cross-correlation tends to be gentle. Therefore, the accuracy of the time difference specified by maximizing the cross-correlation deteriorates.

FIG. 7 shows a fourth example of the configuration of the sound pickup apparatus according to the present invention. In this configuration example, this configuration is basically the same as the configuration of the sound pickup device shown in FIG. 4, but a band filtering unit 36 that extracts a specific band of the output of each microphone constituting the microphone array 22 is provided. The difference is that it is connected between the whitening unit and the correlation calculation unit. The band filtering section 36 usually removes low-frequency signals of 200 Hz or less. Then, the correlation is calculated. If correlation is performed between signals recorded in an environment with low-frequency noise without performing bandpass filtering, a correlation peak due to noise may occur, and an erroneous time difference may be determined.

[0061]

According to the present invention, it is possible to reduce the amount of calculation required for the correlation (power) calculation for determining the delay amount of each delay element, which is performed in the conventional method or apparatus. Becomes The amount of calculation to be reduced varies depending on how the representative position is determined and how the size of the small region S is determined. For example, by setting ten representative positions, ten regions are set. In the case where the setting is made to divide the data into two, it is possible to reduce the number to approximately 1/10 as compared with the conventional method of calculating the correlation for the entire region.

Further, according to the present invention, it is possible to more precisely specify the position of the sound source based on the precisely determined propagation time. For example, by using a general sound source position estimating method when the microphone is in the XY plane as described below, the position of the sound source can be specified more precisely.

Now, the number of microphone arrays is M, the time obtained by dividing the distance between the sound source and the i-th microphone by the speed of sound is t _i (i = 1, 2,..., M), the reference microphone and i th sound waves arrival time difference between the microphones d _{i
(= T i -t 1; (} i = 2, ..., M)), the orthogonal coordinate position of the i-th microphone _{P i (x i, y i} , 0), the orthogonal coordinate position of the sound source Q (x, y, z). In this case, the sound wave arrival time difference d _i is observable value, also a rectangular coordinate position _{P i (x i, y i} , 0) is a value given in advance. From these, the orthogonal coordinate position Q (x,
y, z) can be obtained as follows.

[0064]

(Equation 7)

Is as follows. Also,

(Equation 8)

Is as follows. therefore,

(Equation 9)

The following holds. If we make this a determinant,

(Equation 10)

By solving this determinant, X and Y can be obtained. About Z

[Equation 11]

Assuming that Z> 0,

(Equation 12)

Is satisfied. Thus, Z is obtained. As described above, the sound source coordinate position Q (X, Y, Z) can be obtained.

The equation for obtaining the sound source coordinate position is not limited to the above equation, but can be calculated using an equation based on another general sound source position estimation method.

[Brief description of the drawings]

FIG. 1 is a flowchart schematically showing steps of a sound collection method according to the present invention.

FIG. 2 is a diagram illustrating an example of a correspondence relationship between a representative position, a propagation time, and a range stored in a storage unit.

FIG. 3 is a conceptual diagram showing a relationship between a representative position, a propagation time, and a range thereof.

FIG. 4 is a block diagram illustrating a schematic configuration of a first configuration example of a sound collection device according to the present invention.

FIG. 5 is a block diagram illustrating a schematic configuration of a second configuration example of the sound collection device according to the present invention.

FIG. 6 is a block diagram showing a schematic configuration of a third configuration example of the sound collection device according to the present invention.

FIG. 7 is a block diagram illustrating a schematic configuration of a fourth configuration example of the sound collection device according to the present invention.

FIG. 8 is a diagram for explaining the principle of noise suppression sound collection by the delay-and-sum method.

FIG. 9 is a diagram for explaining that, when the sound source is located at a position close to the microphone array, the gain load at the subsequent stage of the delay unit is appropriately set to improve the sound pickup S / N ratio.

[Explanation of symbols]

1 ... macro Hong array (sound pickup unit) ₂ 1 to 2 _M ... microphone 3 ₁ to 3 _M ... delayer 4 ... adder 5 ... output signal 6 ... delay sum array device 7 ₁ to _7-M ... gain 21 ... Microphone Array Processing device (sound collecting device) 22 ... microphone array 23 ... storage unit 24 ... delay time calculation unit 25 ... sound source position determination unit 26 ... extraction unit 27 ... correlation calculation unit 31 ... whitening unit 36 ... band-pass filter unit

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yutaka Kaneda 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term in Nippon Telegraph and Telephone Corporation (reference) 5D020 BB04

Claims (8)

[Claims] 1. A sound collection method in which sound signals recorded by a plurality of microphones are respectively delayed by independent delay times, and the delay signals are added to obtain a sound pickup signal. Using propagation time recording means for recording a plurality of correspondences between the propagation time of the sound wave to the microphone and the range of the propagation time, the power of the collected sound signal obtained by correcting the delay time with the propagation time is the first power The sound pickup obtained by selecting the representative position corresponding to the propagation time that maximizes the first power, and correcting the delay time for each propagation time belonging to the range of the propagation time corresponding to the representative position Calculate the signal power as a second power, determine a propagation time that maximizes the second power, and output a sound pickup signal obtained by correcting a delay time for the determined propagation time. Sound collection method. 2. A sound collection method in which sound signals recorded by a plurality of microphones are delayed by independent delay times and a sound pickup signal is obtained by adding each of the delayed signals, wherein a sound pickup signal is obtained from a representative position and the sound source position. Using a propagation time recording unit that records a plurality of correspondences between the propagation time of the sound wave to each microphone and the range of the propagation time difference between the microphones, the sound pickup signal obtained by correcting the delay time with the propagation time Calculating a power, selecting a representative position corresponding to the propagation time that maximizes the power, calculating a cross-correlation between the microphones for each propagation time difference belonging to the range of the propagation time difference corresponding to the representative position, A sound collection method that determines a propagation time difference that maximizes correlation, and outputs a sound collection signal obtained by correcting a delay time for the determined propagation time difference. 3. A sound collecting device for delaying an audio signal recorded by a plurality of microphones with an independent delay time and adding a sound signal by adding each of the delayed signals, comprising: a plurality of microphones; A microphone array (22) for converting a sound detected by each of the microphones and outputting a plurality of independent signals, and an independent delay amount connected to an output of the microphone array for each of the plurality of independent signals. In addition, a delay-and-sum array device (6) that generates a sound pickup signal by adding the signals output after adding the delay amount, and outputs the sound pickup signal; A storage unit (23) storing a plurality of correspondences between the propagation time of the sound wave to each microphone and the range of the propagation time, and a delay sum obtained by correcting the delay time with the propagation time A sound source position determination unit that calculates a power of a sound pickup signal from the radar device as a first power and selects a representative position corresponding to a propagation time that maximizes the first power by referring to the storage unit; (25) acquiring the range of the propagation time corresponding to the representative position from the storage unit, and correcting the delay time for each propagation time belonging to the range to obtain the power of the collected signal as the second power. A delay time calculating unit (24) for calculating and determining a propagation time that maximizes the second power, wherein the delay-and-sum array device according to the propagation time determined by the delay time calculating unit And correcting each of the independent delay amounts. 4. A sound collecting device for delaying audio signals recorded by a plurality of microphones with independent delay times, and adding the respective delayed signals to obtain a sound collecting signal, comprising: a plurality of microphones; A microphone array (22) for converting a sound detected by each of the microphones and outputting a plurality of independent signals, and an independent delay amount connected to an output of the microphone array for each of the plurality of independent signals. In addition, a delay-and-sum array device (6) for generating a sound pickup signal by adding the signals output after adding the delay amount, and outputting the sound pickup signal; a representative position, and a sound source position. A storage unit (23) for recording a plurality of correspondences between a propagation time of a sound wave to each of the microphones and a range of a propagation time difference between the microphones; A sound source position determination unit (25) connected to the output, for calculating the power of the picked-up signal obtained by correcting the delay time with the propagation time, and selecting a representative position corresponding to the propagation time that maximizes the power; Calculating the cross-correlation between the microphones for each propagation time difference belonging to the range of the propagation time difference corresponding to the representative position, and determining the propagation time difference that maximizes the cross-correlation;
A delay time calculating unit (24), wherein the delay-and-sum array device corrects each of the independent delay amounts according to the propagation time difference determined by the delay time calculating unit. Sound pickup device. 5. A storage in which a plurality of representative positions, a propagation time of a sound wave from each of the plurality of representative positions to each of the plurality of microphones, and a range of the propagation time are stored in association with each other. A microphone array (22), comprising: a unit (23); a plurality of microphones; converting a sound detected by each of the plurality of microphones to output a plurality of independent signals; and a microphone array (22) connected to an output of the microphone array. Adding a delay amount to each of the plurality of independent signals, adding a signal output with the delay amount added, generating a sound pickup signal, and outputting the sound pickup signal. An array device (6), connected to the output of the picked-up signal of the delay-and-sum array device, and storing the representative position corresponding to the position of the sound source in the storage unit by determining the output. A sound source position determining unit (25) for selecting from the selected representative positions; and a propagation time range corresponding to the representative position stored in the storage unit, based on the representative position selected by the sound source position determining unit. A delay time calculating unit (24) for calculating a delay amount added to each of the plurality of independent signals in the delay-and-sum array device based on the range of the propagation time. The delay amount is estimated by calculating the correlation between the outputs of the microphones within the propagation time range corresponding to the representative position, and the delay amount that maximizes the output of the picked-up signal among the estimated delay amounts The delay sum array device corrects each delay amount of the plurality of delay elements according to the delay amount determined by the delay time calculation unit. . 6. The sound pickup device according to claim 3, wherein the delay time calculation unit uses the information of the distance delay time in a storage unit to calculate the distance delay time of the microphone. A sound collection device comprising: an extraction unit that extracts a signal from the output so as to remove the signal from the output; and a correlation calculation unit that calculates a correlation between outputs of the microphones using a signal extracted by the extraction unit. 7. The sound collection device according to claim 6, wherein the delay time calculation unit is further connected between the extraction unit and the correlation calculation unit, and performs a whitening process on an output from the extraction unit. And a whitening unit for sending a whitened output to the correlation calculating unit. 8. The sound collection device according to claim 7, wherein the delay time calculation unit is further connected between the whitening unit and the correlation calculation unit, and a predetermined band of an output from the whitening unit. And a band filter for supplying the output from which the band has been removed to the correlation calculator.