Microphone position determination method and microphone system

Abstract

The present invention provides a microphone position determination method and a microphone system. The microphone position determination method is a method for determining the positions of a plurality of microphones (11) in a microphone array (1) having a plurality of microphones (11) arranged in a plurality of concentric circles. The microphone position determination method comprises: a constraint condition acquisition step for acquiring a constraint condition for the maximum number of the plurality of microphones (11); and a selection step for selecting a combination of directional characteristics that minimizes the difference from a target value of the directional characteristics of the microphone array (1) from a plurality of combinations of the number of microphones (11) included in each of the plurality of concentric circles and the radius of each of the plurality of concentric circles, wherein the plurality of combinations satisfy the constraint condition.

Description

Technical Field

[0001] The present invention relates to a method for determining positions of a plurality of microphones in a microphone array and a microphone system comprising the microphone array. Background Art

[0002] Conventionally, there are known microphone arrays installed in conference rooms, etc. In the conventional microphone array disclosed in US Pat. No. 9,565,493, a plurality of microphones are arranged on a plurality of concentric circles. Summary of the Invention

[0003] Problems to be solved by the invention

[0004] The configuration of microphones in a conventional microphone array is determined by the designer's experience and intuition. Therefore, the difference between the main lobe and the side lobe in the directional characteristics of the microphone array is insufficient, and the directivity needs to be improved.

[0005] The present invention focuses on this point, and an object of the present invention is to improve the directivity of a microphone array.

[0006] Solutions for solving problems

[0007] A microphone position determination method according to a first aspect of the present invention is a method for determining positions of a plurality of microphones in a microphone array having a plurality of microphones arranged in a plurality of concentric circles.

[0008] The microphone position determination method includes: a constraint condition acquisition step for acquiring a constraint condition including the maximum number of the multiple microphones; and a selection step for selecting a combination of directional characteristics representing the smallest difference from a target value of the directional characteristics of the microphone array from multiple combinations of (i) the number of microphones included in each of the multiple concentric circles and (ii) the radius of each of the multiple concentric circles, wherein the multiple combinations satisfy the constraint condition.

[0009] The selection step may include selecting a combination of the number of microphones included in each of the multiple concentric circles and the radius of each of the multiple concentric circles, which represents a directional characteristic with the smallest difference from the target value, by using a variable vector including the number of microphones included in each of the multiple concentric circles and the radius of each of the multiple concentric circles as a mutation vector used in the differential evolution algorithm.

[0010] The constraint acquisition step may include acquiring the number of a plurality of sound source localization microphones used to specify the direction of the sound source as one of the constraint conditions. The constraint acquisition step may include acquiring the radius of the outermost concentric circle of the plurality of concentric circles as one of the constraint conditions. The constraint acquisition step may include acquiring the number of microphones included in each of the plurality of concentric circles as three or more as one of the constraint conditions.

[0011] The constraint condition acquisition step may include acquiring, as one of the constraint conditions, a target value of a directional characteristic corresponding to a difference between a size of a main lobe and a size of a side lobe of sensitivity to the input sound signal.

[0012] The selection step may include: setting a vector including the number of the multiple concentric circles in which the multiple microphones are configured, the radius of each concentric circle in the multiple concentric circles, and the number of the microphones configured in each concentric circle in the multiple concentric circles as variables as an initial variable vector; calculating an initial objective function value, wherein the initial objective function value is a value representing the error between an ideal value of the directional characteristic of the microphone array and the directional characteristic of the microphone array calculated using the initial variable vector; determining a plurality of updated variable vectors different from the initial variable vector; calculating a plurality of updated objective function values, wherein the plurality of updated objective function values are values representing the error between an ideal value of the directional characteristic of the microphone array and the directional characteristic of the microphone array calculated using the plurality of updated variable vectors, and selecting a combination of the positions of the multiple microphones corresponding to the minimum objective function value from the initial objective function value and the plurality of updated objective function values.

[0013] According to the second aspect of the present invention, the microphone system is a microphone array having multiple microphones arranged on multiple concentric circles, wherein the change in the difference between the radii of two adjacent concentric circles in the multiple concentric circles does not increase monotonically according to the distance relative to the center position of the multiple concentric circles, and the attenuation of the side lobe in the directional characteristic relative to the main lobe is equal to or greater than 10dB.

[0014] The multiple microphones may include: a plurality of positioning microphones, which are arranged at the center position and at multiple positions on the innermost concentric circle closest to the center position among the multiple concentric circles, and are used to specify the direction of the sound source; and a plurality of beamforming microphones, which are arranged on the multiple concentric circles and are used to collect sounds generated from the sound source specified by the multiple positioning microphones.

[0015] Three or six positioning microphones may be arranged at equal intervals on the innermost concentric circle. The distance between two adjacent positioning microphones among the plurality of positioning microphones may be less than or equal to half the minimum wavelength of sound in a frequency band used to specify the direction of the sound source. The distance between two positioning microphones may be less than or equal to 42.5 mm.

[0016] Some of the plurality of microphones may be disposed at a plurality of intersection points where at least one straight line passing through the centers of the plurality of concentric circles intersects each of the plurality of concentric circles.

[0017] The above-mentioned microphone system may also include: an audio processing unit for processing the sound signal output from the microphone array, wherein the audio processing unit may include: a direction specifying unit for specifying the direction of the sound source based on the multiple sound signals input from the multiple positioning microphones; and a sound output unit for outputting a sound synthesized by weighting each of the multiple sounds input to the multiple beamforming microphones based on the direction of the sound source specified by the direction specifying unit.

[0018] Effects of the Invention

[0019] According to the present invention, an effect is achieved in which the microphone array is less likely to collect unnecessary sounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A and 1B Each shows an overview of a microphone system.

[0021] Figure 2 Shows the structure of the microphone array.

[0022] Figure 3 The structure of the audio processing unit is shown.

[0023] Figure 4 This is a flowchart showing an overview of a method for determining the arrangement of multiple microphones.

[0024] Figure 5 The model used in this search example is shown.

[0025] Figure 6 The directional characteristics of the microphone array in the first search example are shown.

[0026] Figure 7 The directional characteristics of the microphone array of the comparative example are shown.

[0027] Figure 8 The directional characteristics of the microphone array in the second search example are shown.

[0028] Figure 9 The directional characteristics of the microphone array in the third search example are shown. DETAILED DESCRIPTION

[0029] [Overview of Microphone System S]

[0030] Figure 1A and 1B An overview of each microphone system S is shown. Figure 2 The structure of the microphone array 1 is shown. The microphone system S includes the microphone array 1 and the audio processing unit 2, and is a device for collecting audio of a plurality of speakers H ( Figure 1A and 1B The microphone system S does not need to include the audio processing section 2 and can be connected to a computer that performs audio processing.

[0031] like Figure 2 As shown by the black circles in FIG, the microphone array 1 includes a plurality of microphones 11 and is installed on the ceiling, wall, or floor of the space where the speaker H is staying. The microphone array 1 inputs a plurality of sound signals to the audio processing unit 2 based on the speech input to the plurality of microphones 11.

[0032] The audio processing unit 2 processes the sound signals output from the microphone array 1 (i.e., the multiple sound signals output from the multiple microphones 11). The audio processing unit 2 analyzes the sound signals input from the microphone array 1 to identify the direction of the speaker H (i.e., the sound source). Furthermore, the audio processing unit 2 performs beamforming processing by adjusting the weighting coefficients of the multiple sound signals corresponding to the multiple microphones 11 based on the direction toward the specified speaker H. This process increases sensitivity to the speech produced by the speaker H over sensitivity to sounds originating from directions other than the speaker H.

[0033] Figure 1A The state in which the speaker H-2 is speaking is shown. Figure 1B Shows the state where speaker H-3 is speaking. Figure 1A In the state shown, the audio processing unit 2 performs beamforming processing so that the main lobe in the directional characteristics of the microphone array 1 points to the speaker H-2. In this case, the audio processing unit 2 synthesizes multiple sound signals by, for example, assigning a greater weight to the sound signal output from the microphone 11 at a position near the speaker H-2 than to the sound signals output from the other microphones 11. Figure 1BIn the state shown, the audio processing unit 2 performs beamforming processing so that the main lobe in the directional characteristics of the microphone array 1 is directed toward the speaker H-3. In this case, the audio processing unit 2 synthesizes multiple sound signals by, for example, assigning a greater weight to the sound signal output from the microphone 11 located near the speaker H-3 than to the sound signals output from the other microphones 11.

[0034] In microphone array 1, multiple microphones 11 are arranged so that the difference between the main lobe and the side lobe in the directional characteristics is equal to or greater than 10 dB due to the beamforming processing performed by audio processing section 2. Next, the structure of microphone array 1 and the method for determining the arrangement of multiple microphones 11 will be described in detail.

[0035] [Structure of Microphone Array 1]

[0036] like Figure 2 As shown by the black circles in FIG, the microphone array 1 includes a plurality of microphones 11 arranged on a plurality of (for example, more than four) concentric circles. In the microphone array 1, a plurality of microphones 11 are provided for each of the four concentric circles C1, C2, C3, and C4. Concentric circle C1 is the innermost concentric circle, and three microphones 11 are provided on concentric circle C1. The three microphones 11b (11b-1, 11b-2, and 11b-3) provided on concentric circle C1 are used as: (i) a sound source localization microphone 11 for specifying a direction toward the position of the speaker H as the sound source; and (ii) a beamforming microphone 11 for collecting the speech produced by the speaker H.

[0037] Concentric circle C2 is the second concentric circle from the inner side, and four microphones 11c are arranged on concentric circle C2. Concentric circle C3 is the third concentric circle from the inner side, and seven microphones 11d are arranged on concentric circle C3. Concentric circle C4 is the outermost concentric circle. Seventeen microphones 11e are arranged on concentric circle C4. The microphones 11 arranged on concentric circles C2, C3, and C4 serve as beamforming microphones 11. It should be noted that Figure 2 In FIG. 1 , only the microphone 11 arranged on the straight line L among the plurality of microphones 11 c , 11 d , and 11 e is denoted by a reference numeral.

[0038] As described in detail below, the radii of the four concentric circles C1, C2, C3, and C4 and the number and positions of the microphones 11 included in each concentric circle are determined by searching for the optimal directional characteristics. As a result, the amount of change in the difference between the radii of two adjacent concentric circles among the four concentric circles C1, C2, C3, and C4 is determined so that the amount of change does not monotonically increase according to the distance from the center position of the plurality of concentric circles.

[0039] Specifically, in Figure 2 In the illustrated microphone array 1, the radius of concentric circle C1 is 0.03856 m, the radius of concentric circle C2 is 0.10660 m, the radius of concentric circle C3 is 0.14024 m, and the radius of concentric circle C4 is 0.21500 m. The difference between the radii of concentric circles C1 and C2 is 0.06804 m, the difference between the radii of concentric circles C2 and C3 is 0.03364 m, and the difference between the radii of concentric circles C3 and C4 is 0.07476 m, and these differences do not increase monotonically with distance from the center of the concentric circles. Furthermore, the attenuation of the side lobes relative to the main lobe in the directional characteristics of microphone array 1 is -14.8 dB, achieving sufficient directivity. As described in detail below, microphone array 1 exhibits this excellent directional characteristic because the configuration of the plurality of microphones 11 is determined using an algorithm for searching for the optimal configuration of the plurality of microphones 11.

[0040] Among the multiple microphones 11 included in the microphone array 1, (i) the microphone 11a arranged at the center position of the multiple concentric circles and (ii) the three microphones 11b (11b-1, 11b-2, and 11b-3) arranged at equal intervals on the innermost concentric circle C1 closest to the center position are used as multiple sound source localization microphones 11 for specifying the position of the sound source. The other microphones 11 included in the microphone array 1 are used as multiple beamforming microphones 11 for collecting sounds generated from the sound sources at the positions specified by the sound source localization microphones 11. The microphone 11a and the microphones 11b-1 to 11b-3 can also be used as beamforming microphones 11. In other words, the microphone 11a and the microphones 11b-1 to 11b-3 can be used for two purposes: sound source localization and beamforming.

[0041] The distance between two adjacent sound source localization microphones 11 among the plurality of microphones 11 serving as the sound source localization microphones 11 is less than or equal to half the minimum wavelength of sound in a frequency band for specifying the direction toward the position of the speaker H serving as the sound source. When the distance between the two sound source localization microphones 11 is set in this manner, aliasing does not occur, thereby improving the accuracy of estimating the direction toward the speaker H.

[0042] When the frequency range including the main frequency component of the voice of the presumed speaker H is equal to or higher than 500 Hz and equal to or lower than 4000 Hz, the distance D between two adjacent sound source localization microphones 11 is preferably 42.5 mm or less. This is because the wavelength of sound with a frequency of 4000 Hz is 85 mm. When the frequency range including the main frequency component of the voice of the presumed speaker H is equal to or higher than 500 Hz and equal to or lower than 5000 Hz, the distance D is preferably 34 mm or less. This is because the wavelength of sound with a frequency of 5000 Hz is 68 mm. It should be noted that if the distance D is too small, the difference in the sounds entering each sound source localization microphone 11 becomes too small. For this reason, the distance D is preferably, for example, 30 mm or more and 40 mm or less.

[0043] In addition, some microphones 11 are provided at a plurality of intersections where at least one straight line L passing through the centers of the plurality of concentric circles C1, C2, C3 and C4 intersects with the respective concentric circles C1, C2, C3 and C4. Figure 2 In the illustrated example, the microphones 11a, 11b-1, 11c, 11d, and 11e are arranged on the same straight line L. That is, one of the microphones 11 arranged on the concentric circle C1, one of the microphones 11 arranged on the concentric circle C2, one of the microphones 11 arranged on the concentric circle C3, and one of the microphones 11 arranged on the concentric circle C4 are arranged on the same straight line L as one of the microphones 11 arranged on the other concentric circles.

[0044] Since the microphone array 1 is configured in this manner, the accuracy of audio processing for enhancing the directivity toward the speaker H is improved, and the load of the audio processing is reduced. In addition, since the positional relationship of the plurality of microphones 11 becomes clearer, the accuracy of specifying the direction toward the speaker H is improved.

[0045] [Configuration of the Audio Processing Unit 2]

[0046] Figure 3 2 shows a configuration of the audio processing section 2. The audio processing section 2 includes an AD converter 21, an AD converter 22, a direction specifying section 23, and a sound output section 24.

[0047] The AD converter 21 converts a plurality of sound signals based on the sound entering the plurality of sound source localization microphones 11 into a plurality of sound source localization digital data. The AD converter 21 inputs the converted sound source localization digital data to the direction specifying unit 23. The AD converter 22 converts a plurality of sound signals based on the sound entering the plurality of beamforming microphones 11 ( Figure 3The AD converter 21 and the AD converter 22 convert the plurality of sound signals of the sound ("BF" in the figure) into a plurality of beamformed digital data. The AD converter 22 inputs the converted beamformed digital data to the sound output unit 24. The AD converters 21 and 22 may be composed of a plurality of devices or a single device.

[0048] The direction specifying unit 23 specifies the direction toward the location of the speaker H, which is the sound source, based on the plurality of sound signals input from the plurality of sound source localization microphones 11. Specifically, the direction specifying unit 23 specifies the direction toward the speaker H based on the plurality of sound source localization digital data input from the AD converter 21. The direction specifying unit 23 specifies the direction toward the speaker H based on, for example, the relationship between the loudness of the sounds represented by the plurality of sound source localization digital data. The direction specifying unit 23 notifies the sound output unit 24 of the direction toward the specified speaker H.

[0049] The sound output unit 24 outputs a synthesized sound by weighting each of the multiple sounds input to the beamforming microphones 11 based on the direction toward the speaker H specified by the direction specifying unit 23. Specifically, the sound output unit 24 generates a plurality of multiplied values by multiplying each of the beamforming digital data corresponding to each microphone 11 by a weighting coefficient determined based on the direction toward the speaker H, thereby adding the generated multiplied values to output the synthesized sound. For example, the absolute value of the weighting coefficient for the microphone 11 at the position corresponding to the direction toward the speaker H is set to a value greater than the absolute value of the weighting coefficient for the microphone 11 at other positions. Since the direction specifying unit 23 and the sound output unit 24 operate in this manner, the reproducibility of the sound produced by the speaker H is improved regardless of the direction toward the speaker H.

[0050] Since the directional characteristics of the microphone array 1 differ depending on the arrangement of the plurality of microphones 11, the quality of the sound synthesized by the sound output unit 24 is affected by the arrangement of the plurality of microphones 11. Next, a method for determining the arrangement of the plurality of microphones 11 for improving the quality of the sound synthesized by the sound output unit 24 will be described in detail.

[0051] [Overview of a method for determining the arrangement of the plurality of microphones 11]

[0052] Figure 4 This is a flowchart showing an outline of a method for determining the configuration of the plurality of microphones 11. As an example, the configuration search device includes a computer, and executes a program, uses Figure 4 The microphone position determination method shown in the flowchart of FIG. 1 determines the configuration of the plurality of microphones 11. Figure 4According to the method shown in the flowchart, a configuration search device determines the optimal configuration of multiple microphones 11 when a sound source is in a specific direction. The configuration search device changes the direction of the sound source (i.e., the direction toward the location of the sound source) to a plurality of different directions to determine the optimal configuration of multiple microphones 11 for each direction. The configuration search device determines the configuration of multiple microphones 11 that is as suitable as possible for each direction in which the multiple sound sources are located, for example, by using the least squares method.

[0053] Below, we will refer to Figure 4 The following describes a process in which the configuration search device determines the configuration of the plurality of microphones 11. The configuration search device determines the configuration of the plurality of microphones 11 using, for example, a differential evolution (DE) method as a differential evolution algorithm or a JADE method as an improved DE method.

[0054] In order to determine the configuration of the plurality of microphones 11, the configuration search apparatus first acquires constraint conditions (step S1). For example, the configuration search apparatus displays a screen for inputting constraint conditions on a display and acquires the constraint conditions input on the screen.

[0055] The configuration search device, for example, obtains the maximum number of multiple microphones 11 as one of the constraints. The configuration search device may obtain the number of sound source localization microphones 11 and the radius of the outermost concentric circle among the multiple concentric circles as one of the constraints. Because the configuration search device obtains these constraints, the time required to determine a configuration of multiple microphones 11 that meets the size and cost requirements of the microphone array 1 can be shortened. The configuration search device may obtain the number of microphones 11 included in each of the multiple concentric circles to be three or more as one of the constraints. By having three or more microphones 11 in a concentric circle, variations in directional characteristics caused by the direction of the sound source can be reduced.

[0056] Subsequently, the configuration search device acquires a target value for the directional characteristic of the microphone array 1 (step S2). The directional characteristic of the microphone array 1 is represented by a value corresponding to the difference between (i) the size of the main lobe of sensitivity to the input sound signal and (ii) the size of the side lobe of sensitivity to the input sound signal. For example, the directional characteristic of the microphone array 1 is represented as the attenuation amount of the side lobe relative to the main lobe when a predetermined sound is input to the microphone array 1. For example, the configuration search device displays a screen for inputting the target value on a display and acquires the target value input on the screen.

[0057] Next, the configuration search device uses the JADE method to determine an initial variable vector (step S3) for starting a search for an optimal configuration of the plurality of microphones 11. For example, the configuration search device sets a vector including the number of concentric circles in which the microphones 11 are arranged, the radius of each concentric circle, and the number of microphones 11 in each concentric circle as variables as the initial variable vector.

[0058] Subsequently, the configuration search device calculates the target function value (i.e., the initial target function value) using the determined initial variable vector (step S4), and temporarily stores the calculated target function value as a reference function value in association with the initial variable vector (step S5). The target function value is a value representing the error between the ideal value of the directional characteristics of the microphone array 1 and the directional characteristics of the microphone array 1 calculated using the initial variable vector. The smaller the target function value, the better the directional characteristics.

[0059] Next, the configuration search device determines an updated variable vector (step S6). The updated variable vector is a variable vector that changes at least one variable included in the initial variable vector. The configuration search device determines the updated variable vector by setting at least one of (i) the number of concentric circles in which microphones 11 are arranged, (ii) the radius of each concentric circle, and (iii) the number of microphones 11 in each concentric circle to a value different from that of the initial variable vector. The configuration search device uses, for example, a differential evolution algorithm to determine the updated variable vector.

[0060] The configuration search device uses a variable vector including, for example, the number of microphones 11 included in each of the plurality of concentric circles and the radius of each of the plurality of concentric circles as an update variable vector, which is a mutant vector used in a differential evolution algorithm. The configuration search device selects a combination of directional characteristics that minimizes the difference from a target value of the directional characteristics from a plurality of combinations of (i) the number of microphones 11 included in each of the plurality of concentric circles and (ii) the radius of each of the plurality of concentric circles, wherein the plurality of combinations satisfies a constraint condition.

[0061] Specifically, the configuration search device first calculates the objective function value when using the updated variable vector (step S7). The configuration search device compares the calculated objective function value with the objective function value stored in step S5 (step S8). If the calculated objective function value is equal to or greater than the stored reference function value ("Yes" in step S8), the configuration search device causes the configuration determination process to proceed to step S10. If the calculated objective function value is less than the stored objective function value ("No" in step S8), the configuration search device stores the calculated objective function value (i.e., the updated objective function value) as a new reference function value in association with the updated variable vector (step S9).

[0062] Next, the configuration search device determines whether the target function value has been calculated a predetermined number of times (step S10). In other words, the configuration search device determines whether the target function value has been calculated for a predetermined number of variable vectors. The predetermined number of times is, for example, set by the designer of microphone array 1. If the target function value has been calculated the predetermined number of times ("Yes" in step S10), the configuration search device determines that the configuration represented by the variable vector stored in association with the reference function value is the configuration of the plurality of microphones 11 and terminates the process.

[0063] If the number of objective function value calculations has not reached the predetermined number ("No" in step S10), the configuration search device returns the configuration determination process to step S6. By executing the selection steps of steps S7 to S10 in this manner, the configuration search device selects the optimal combination of directional characteristics that minimizes the difference from the target value of the directional characteristics from the multiple combinations of microphone 11 positions that satisfy the constraint conditions (step S11). In other words, the configuration search device selects the combination of microphone 11 positions that corresponds to the minimum objective function value from the initial objective function value and the multiple updated objective function values.

[0064] [Example of searching for the optimal configuration using the JADE method]

[0065] The following description shows an example of searching for an optimal arrangement of the plurality of microphones 11 using the JADE method. Figure 4 The configuration search device executes the program shown in the flowchart to perform the following design process. The JADE method uses an algorithm that enhances the global searchability of the DE method to automatically adjust parameters for each problem. Therefore, even for problems with multimodal objective functions, such as those involving the determination of the configuration of multiple microphones 11, the configuration search device can achieve a good search using the JADE method.

[0066] Figure 5 The model used in this search example is shown in Figure 5As shown, in a space defined by the x-axis, y-axis, and z-axis, the sound source, which is a prerequisite for searching for the optimal arrangement of the plurality of microphones 11, forms an angle θ with the x-axis in the xy plane and an angle Φ from the xy plane to the z-axis. In other words, the arrangement search device searches for an arrangement of the plurality of microphones 11 that optimizes directivity when the microphone array 1 receives sound from a sound source located in the (θ, Φ) direction relative to the origin.

[0067] Assume that the total number of concentric circles is P and the radius of each concentric circle is r p , and the number of microphones 11 arranged in each concentric circle is M p (p=1,2,...,P). If the distance between the sound source and the microphone array 1 is relative to the radius r of the largest concentric circle P If is large enough, the sound signal generated by the sound source is considered to be a plane wave near the microphone array 1. In this case, the sound receiving signal z of the mth microphone 11 on a concentric circle p is pm (n) The sound receiving signal z of the microphone 11 on the x-axis can be based on the concentric circles. p,xaxis (n), using arrival time difference τ pm (θ, Φ) is expressed by the following formula.

[0068] [Formula 1]

[0069]

[0070] [Formula 2]

[0071]

[0072] [Formula 3]

[0073]

[0074] Here, c is the speed of sound. In this case, the directivity G (θ, Φ, ω) corresponding to the size of the main lobe of the microphone array 1 is k ) can be expressed by the following formula.

[0075] [Formula 4]

[0076]

[0077] Delay and beamformer weight coefficient w * pm，k It can be expressed by the following formula.

[0078] [Formula 5]

[0079]

[0080] The design problem related to the optimal arrangement of the plurality of microphones 11 can be replaced by searching for a method that can obtain the desired directivity D (θ, Φ, ω) with the desired directivity being used as the target value. k ) close to the directivity G(θ, Φ, ω k ) is a problem of the configuration of the microphone 11. The error E(θ, Φ, ω) used in the search k ) can be expressed by the following formula.

[0081] [Formula 6]

[0082] E(θ,φ,ω k )=|D(θ,φ,ω k )-G(θ,φ,ω k )|

[0083] The optimal configuration can be specified by obtaining a variable vector that minimizes the maximum error on the approximation band as shown below.

[0084] [Formula 7]

[0085] min maxE(θ,φ,ω k )

[0086] M p , r p θ∈Θ

[0087] φ∈Φ

[0088] ω k ∈Ω

[0089] Here, in order to obtain a variable vector that minimizes the maximum error by using the JADE method, the configuration search device first initializes N solution groups X using uniform random numbers within the domain range of the search space. i (i=1, 2, ..., N), and calculate the objective function value of each individual. The configuration search device generates differential mutation individuals, sub-individuals and evolutionary individuals up to a maximum generation I, and searches for the minimum solution of the objective function.

[0090] In order to apply the JADE method to the microphone configuration design problem, the variable vector x is defined as follows:

[0091] [Formula 8]

[0092] x=[M1,…,M P , r1,…,r P ] T

[0093] Here, in order to ensure that the configuration is not determined to be an impossible configuration, the number of microphones 11 is kept at the maximum achievable number M. max The constraints within are defined as follows:

[0094] [Formula 9]

[0095]

[0096] In the microphone system S, the sound source localization process is performed before the beamforming process. Therefore, when determining the arrangement of the plurality of microphones 11, the arrangement of the sound source localization microphones 11 must also be considered. Figure 2 As shown, a concentric circle is arranged at the center position of the concentric circle and three or six sound source localization microphones 11 are arranged in the innermost concentric circle C1, and the following constraints are added:

[0097] [Equation 10]

[0098] M1=1, M2={3, 6},

[0099] When the maximum radius of the outermost concentric circle is R max When the radius r of each concentric circle p The constraints are expressed as follows:

[0100] [Equation 11]

[0101] r1=0、r P =R max 、r p-1 <r p

[0102] In this case, the variable vector x′ to be obtained is expressed as follows:

[0103] [Equation 12]

[0104] x′=[1,M2,…,M P , r2,…,r p-1 , R max ] T

[0105] Therefore, the design problem of configuring multiple microphones 11 is formulated as a mixed integer planning problem as shown below:

[0106] [Equation 13]

[0107] minδ、sub.toE(θ s ,φ s ,ω k )≤δ

[0108] [Equation 14]

[0109] r p-1 <r p M2 = {3, 6}

[0110] [Equation 15]

[0111]

[0112] Here, θ s and Φ s (s=1, . . . , S) represents a discrete direction, and δ represents a maximum error in the approximation band of Equation 6. When searching for the optimal configuration by the JADE method, the following enlarged objective function f(x′) using this δ is used.

[0113] [Equation 16]

[0114]

[0115] Here, λ u (x′) (u=1, . . . , 4) represents a penalty function. λ1(x′) is a penalty function for limiting the maximum number of microphones 11 .

[0116] [Equation 17]

[0117]

[0118] [Equation 18]

[0119]

[0120] λ2(x′) is a penalty function of the number of sound source localization microphones 11 .

[0121] [Equation 19]

[0122]

[0123] λ3(x′) is a penalty function for preventing the number of microphones 11 arranged in each concentric circle from being two or less.

[0124] [Equation 20]

[0125]

[0126] λ4(x') is a penalty function for arranging the radii in ascending order. α>0 is a constant for preventing the difference between the radii of adjacent concentric circles from being zero.

[0127] [Equation 21]

[0128]

[0129] [First search example]

[0130] In this search example, for simplicity, Φ L = 0[rad]. Set the desired directivity D(θ,ωk ) is set as shown below.

[0131] [Equation 22]

[0132]

[0133] Here, θ S1 and θ S2 is the direction of the main lobe boundary. In this search example, θ S1 =-π / 3[rad],θ S2 =π / 3[rad], direction of sound source θ L = 0 [rad], and the speed of sound c = 343 [m / s]. In the JADE method, μ F and μ CR The initial value of is 0.5, and P best is 0.05.

[0134] As a result of using a computer as a configuration search device and using the JADE method to determine the configuration of the plurality of microphones 11 under the above conditions, the design Figure 2 The microphone array 1 shown. In the microphone array 1, the radius of each concentric circle and the number of microphones 11 in each concentric circle are shown in Table 1.

[0135] [Table 1]

[0136] Radius [m] Number of microphones 0 1 0.03856 3 0.10660 4 0.14024 7 0.21500 17

[0137] Figure 6 The microphone array 1 (ie, Figure 2 The directional characteristics of the microphone array 1) are shown. Figure 6 The directional characteristics of the sound at the following frequencies are shown: 500Hz, 700Hz, 1000Hz, 2000Hz and 4000Hz. Figure 6 In the figure, the maximum value of the main lobe is represented as 0dB.

[0138] As a comparative example, Table 2 shows the radius of each concentric circle of a microphone array in which the microphones 11 are arranged and the number of microphones 11 in each concentric circle when the JADE method is not used. Figure 7 The directional characteristics of the microphone array of the comparative example are shown.

[0139] [Table 2]

[0140] Radius [m] Number of microphones 0 1 0.03 6 0.06 9 0.12 6 0.18 10

[0141] By comparison Figure 6 and Figure 7 , confirm Figure 6 The directional characteristics shown are similar to Figure 7The directional characteristics shown in the figure are more directional than those shown in the figure. Figure 6 In the directional characteristics shown, the minimum attenuation of the side lobe relative to the main lobe is 14.8dB, while Figure 7 In the directional characteristics shown, the minimum value of the attenuation of the side lobe with respect to the main lobe is 5 dB. This confirms that the use of the JADE method to determine the arrangement of the plurality of microphones 11 is effective.

[0142] [Second search example]

[0143] Table 3 shows the radius of each concentric circle and the number of microphones 11 in each concentric circle determined using the JADE method under the conditions that the number of microphones 11 is 48 and the maximum radius of the concentric circle is 0.215 [m].

[0144] [Table 3]

[0145] Radius [m] Number of microphones 0 1 0.04070 3 0.09592 8 0.17148 16 0.21500 20

[0146] Figure 8 The directional characteristics of the microphone array 1 in the second search example are shown. Figure 8 In the directional characteristics shown, the minimum attenuation of the side lobe relative to the main lobe is 16.1dB. Figure 8 The directional characteristics shown are similar to Figure 7 The directional characteristics shown are more directional than those shown.

[0147] [Third search example]

[0148] Table 4 shows the radius of each concentric circle and the number of microphones 11 in each concentric circle determined using the JADE method under the conditions that the number of microphones 11 is 64 and the maximum radius of the concentric circle is 0.215 [m].

[0149] [Table 4]

[0150] Radius [m] Number of microphones 0 1 0.04718 3 0.08322 5 0.10001 9 0.15456 8 0.21500 38

[0151] Figure 9 The directional characteristics of the microphone array 1 in the third search example are shown. Figure 9 In the directional characteristics shown, the minimum attenuation of the side lobe relative to the main lobe is 17.4dB. Figure 9 The directional characteristics shown are similar to Figure 7 The directional characteristics shown are more directional than those shown.

[0152] The microphone array 1 designed using the JADE method has the following common features:

[0153] (1) the amount of change in the difference between the radii of two adjacent concentric circles among the plurality of concentric circles does not monotonically increase according to the distance from the center position of the plurality of concentric circles; and

[0154] (2) The attenuation of the side lobe relative to the main lobe in the directivity characteristic is greater than or equal to 10 dB. When the microphone array 1 has these characteristics, the microphone array 1 preferentially collects sounds generated by sound sources that should be collected and makes it difficult to collect unnecessary sounds.

[0155] [Modification]

[0156] The example in which three sound source localization microphones 11 are arranged at equal intervals on the innermost concentric circle C1 is shown above, but six sound source localization microphones 11 may be arranged at equal intervals on the innermost concentric circle C1 .

[0157] The present invention is described based on typical embodiments. The technical scope of the present invention is not limited to the scope described in the above embodiments, and various changes and modifications can be made within the scope of the present invention. For example, the specific embodiments of the dispersion and integration of the equipment are not limited to the above embodiments, and any units that are functionally or physically dispersed or integrated can be used to constitute all or part of these embodiments. In addition, new typical embodiments generated by any combination of the above embodiments are included in the typical embodiments of the present invention. In addition, the effects of the new typical embodiments brought about by these combinations will also have the effects of the original typical embodiments.

[0158] Reference numerals

[0159] 1 microphone array

[0160] 2 Audio processing unit

[0161] 11 Microphone

[0162] 21 AD converter

[0163] 22 AD converters

[0164] 23 Direction Designation Department

[0165] 23 Sound output unit

Claims

1. A method for determining the positions of a plurality of microphones in a microphone array having a plurality of microphones arranged in a plurality of concentric circles, wherein the plurality of microphones includes a plurality of positioning microphones for specifying the direction of a sound source and a plurality of microphones other than the plurality of positioning microphones, the method comprising: a display step for displaying a screen for inputting constraint conditions, wherein the constraint conditions are used to determine the positions of the plurality of microphones; a constraint condition acquisition step for acquiring the constraint condition input on the screen, the constraint condition including a maximum number of the plurality of microphones and the following condition: the number of the plurality of positioning microphones is equal to or greater than three and at least three of the plurality of positioning microphones are arranged at triangle vertices on one of the plurality of concentric circles; and A selection step for selecting, from a plurality of combinations of the number of microphones included in each of the plurality of concentric circles and the radius of each of the plurality of concentric circles, a combination of directional characteristics representing the smallest difference from a target value of the directional characteristics of the microphone array, wherein the plurality of combinations satisfy the constraint condition.

2. The method for determining microphone positions according to claim 1, wherein: The selection step includes selecting a combination of the number of microphones included in each of the multiple concentric circles and the radius of each of the multiple concentric circles, which represents a directional characteristic with the smallest difference from the target value, by using a variable vector including the number of microphones included in each of the multiple concentric circles and the radius of each of the multiple concentric circles as a mutation vector used in the differential evolution algorithm.

3. The microphone position determination method according to claim 1 or 2, wherein: The constraint condition acquisition step includes acquiring the number of a plurality of positioning microphones for specifying the direction of the sound source as one of the constraint conditions.

4. The microphone position determination method according to claim 1 or 2, wherein: The constraint condition acquisition step includes acquiring the radius of the outermost concentric circle among the multiple concentric circles as one of the constraint conditions.

5. The microphone position determination method according to claim 1 or 2, wherein: The constraint condition acquisition step includes acquiring, as one of the constraint conditions, that the number of microphones included in each of the plurality of concentric circles is three or more.

6. The method for determining microphone positions according to claim 1 or 2, wherein: The constraint condition acquisition step includes acquiring, as one of the constraint conditions, a target value of a directional characteristic corresponding to a difference between a size of a main lobe and a size of a side lobe of sensitivity to an input sound signal.

7. The microphone position determination method according to claim 1 or 2, wherein: The selection step includes: setting a vector including, as variables, the number of the plurality of concentric circles in which the plurality of microphones are arranged, the radius of each of the plurality of concentric circles, and the number of the microphones arranged in each of the plurality of concentric circles as an initial variable vector; calculating an initial objective function value, the initial objective function value being a value representing an error between an ideal value of the directional characteristic of the microphone array and the directional characteristic of the microphone array calculated using the initial variable vector; determining a plurality of updated variable vectors different from the initial variable vector; calculating a plurality of updated objective function values, the plurality of updated objective function values being values representing errors between ideal values of the directional characteristics of the microphone array and the directional characteristics of the microphone array calculated using the plurality of updated variable vectors, and A combination of the positions of the plurality of microphones corresponding to a minimum objective function value is selected from the initial objective function value and the plurality of updated objective function values.

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