JP2017055156A - Sound field measurement device, sound field measurement method, program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound field measurement technique for measuring a sound field accurately by using the spherical wave spectra of multiple spherical microphone arrays.SOLUTION: A sound field measurement device includes a closest microphone determination unit for determining a spherical microphone array closest to the origin of a coordinate system Oby using the arrangement position of the spherical microphone array, a relative power error calculation unit for calculating the relative power error at the arrangement position of the spherical microphone array closest to the origin of the coordinate system O, and a spherical microphone array identifier selection unit for determining a spherical microphone array, becoming a predetermined range indicating that the relative power error is small, as the spherical microphone array for use in calculation of interconversion matrix T(k).SELECTED DRAWING: Figure 7

Description

  The present invention relates to a sound field measurement technique, and more particularly to a technique for measuring a wide range of sound fields using a plurality of spherical microphone arrays.

  In recent years, the audio reproduction technology has been expanded from 2-channel stereo to 5.1-channel reproduction, and further research and development of 22.2 channel reproduction and wavefront synthesis methods are underway. The purpose is to greatly improve the realism of reproduction itself and to expand the reproduction area with high realism as much as possible.

  In order to evaluate and verify such a multi-channel audio reproduction method, it is important to measure the reproduced sound field. For example, in the wavefront synthesis method, it is necessary to compare the actually recorded sound field with the reproduced sound field and grasp the difference. The reason is that various factors such as signal processing for converting the recorded sound field into a playback signal, encoding and decoding of the recorded signal, and acoustic characteristics of the room where the playback device is installed affect the reproduction accuracy of the sound field. . In order to establish a method with high sound field reproduction accuracy, it is important to first accurately measure the sound field.

There are several conventional methods for measuring sound fields. Hereinafter, a conventional method will be described.
(Prior art 1)
In the first method, microphones are densely arranged at regular intervals in an area to be measured, and a sound field is measured. In this method, for example, if microphones are arranged on a two-dimensional grid consisting of 20 vertical and horizontal points, 400 microphones are required. The number of microphones and associated cables is large and at the same time occupies a considerable volume in the area. From the viewpoint of the sound field, a lot of microphones and cables themselves become disturbance factors of the sound field, and the difference between the actually measured sound field and the original desired sound field, that is, the sound field without a measurement system, cannot be ignored. End up.
(Prior art 2)
The following method is a method of concentrating microphones locally in a part of the target measurement area and estimating the sound field of the entire measurement area from the measurement result. As such a method, a sound field measurement method using a spherical microphone array has been proposed (Non-Patent Document 1). The spherical microphone array is a microphone array configured by arranging several tens or more microphone elements on a spherical surface having a radius of several centimeters to several tens of centimeters.

Hereinafter, the method described in Non-Patent Document 1 will be described. The method described in Non-Patent Document 1 measures a sound field generated by a sound source outside the measurement area, that is, handles an internal problem. A coordinate system having the origin of the arrangement position of the spherical microphone array (the center of the spherical microphone array) is represented by O _0, and the coordinates of the point x are represented by polar coordinates (r, θ, φ). At this time, the sound field at the frequency f at the point x of the polar coordinates (r, θ, φ), that is, the sound field S (x, k) at the corresponding wave number k = 2πf / c (where c is the speed of sound). Is

It can be expressed as Here, j _n (•) is an nth-order spherical Bessel function, and Y _nm (•) is a spherical harmonic function of order n and m. Further, a ⁽⁰⁾ _nm (k) is called a spherical wave spectrum and is a coefficient representing a sound field in the coordinate system O ₀ for each frequency (for each wave number). a ⁽⁰⁾ _nm (k) is also referred to as a sound field coefficient.

Therefore, if a ⁽⁰⁾ _nm (k) is known, the sound field can be obtained in a certain range near the origin of the coordinate system O ₀ (that is, the arrangement position of the spherical microphone array) by using (Equation 1). it can.

Hereinafter, an outline of the sound field measuring apparatus 800 of Non-Patent Document 1 will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a sound field measuring apparatus 800 of Non-Patent Document 1. FIG. 2 is a flowchart showing the operation of the sound field measuring apparatus 800 of Non-Patent Document 1. As shown in FIG. 1, the sound field measuring apparatus 800 of Non-Patent Document 1 includes a short-time Fourier transform unit 810 and a spherical wave spectrum calculation unit 820. A spherical microphone array 850 for recording a sound field is outside the sound field measuring apparatus 800. The sound field measuring apparatus 800 of Non-Patent Document 1 obtains a spherical wave spectrum a ⁽⁰⁾ _nm (k) from a collected sound signal recorded using a spherical microphone array 850.

The short-time Fourier transform unit 810 performs frequency by short-time Fourier transform from the collected sound signal recorded using the spherical microphone array 850, that is, the signal collected by each microphone element arranged on the spherical surface of the spherical microphone array 850. An area signal is calculated (S810). The spherical wave spectrum calculation unit 820 calculates the spherical wave spectrum a ⁽⁰⁾ _nm (k) from the frequency domain signal (S820).

Hereinafter, the processing in the spherical wave spectrum calculation unit 820 will be described in detail.
And the radius of the spherical microphone array 850 and _{r 0,} the point x on the sphere of radius _{r 0 (r 0,} theta, phi) sound field S (x, k), from (Equation 1)

It is described.
Here, the spherical harmonic function Y _nm (·)

The orthogonal relationship is established. From (Formula 2) and (Formula 3)

Is obtained. Theoretically, by calculating the integral, the spherical wave spectrum a ⁽⁰⁾ _nm (k) can be obtained. In practice, however, the sound pickup of the microphone elements arranged on the spherical surface of the spherical microphone array 850 is obtained. The spherical wave spectrum a ⁽⁰⁾ _nm (k) must be obtained from the signal. Therefore, assuming that the number of the microphone elements is D, the polar coordinates of the position x _d of the microphone elements are (r ₀ , θ _d , φ _d ) (1 ≦ d ≦ D), and the integral is replaced with a sum of products to obtain a spherical wave spectrum a ⁽⁰⁾ _nm (k) is obtained.

Here, w _d is an appropriately set weight.

As described above, the process of calculating the spherical wave spectrum a ⁽⁰⁾ _nm (k) using (Equation 4) is the process performed by the spherical wave spectrum calculation unit 820.
(Prior art 3)
As described above, the spherical microphone array mostly has a radius of several centimeters to several tens of centimeters, and the range of the sound field that can be measured often remains within several tens of centimeters. Thus, in order to measure a wider sound field, a method has been proposed in which a plurality of spherical microphone arrays are arranged in a distributed manner and the sound field is estimated therefrom (Non-patent Document 2). According to this method, it is possible to measure the sound field at the intermediate position between the spherical microphone array and the spherical microphone array, and it is possible to measure a wide range of sound fields while keeping the number of spherical microphone arrays small. .

  Hereinafter, the method described in Non-Patent Document 2 will be described. Similarly to the method described in Non-Patent Document 1, the method described in Non-Patent Document 2 measures a sound field generated by a sound source outside the measurement area, that is, handles an internal problem.

  Hereinafter, an outline of the sound field measuring apparatus 900 of Non-Patent Document 2 will be described with reference to FIGS. In addition, the same number is attached | subjected to the structure part which has the same function, and duplication description is abbreviate | omitted. FIG. 3 is a block diagram showing a configuration of the sound field measuring apparatus 900 of Non-Patent Document 2. FIG. 4 is a flowchart showing the operation of the sound field measuring apparatus 900 of Non-Patent Document 2. As shown in FIG. 3, the sound field measuring apparatus 900 of Non-Patent Document 2 includes a short-time Fourier transform unit 810, a spherical wave spectrum calculation unit 820, a position measurement unit 910, a T calculation unit 920, and an integration unit 930. Including. A spherical microphone array 850 for recording the sound field is outside the sound field measuring apparatus 900. Further, the short-time Fourier transform unit 810 and the spherical wave spectrum calculation unit 820 have the same number as the spherical microphone array 850 corresponding to the spherical microphone array 850. It is assumed that there are Q spherical microphone arrays 850, and an identifier q is assigned to identify each of them (Q is an integer of 1 or more, 1 ≦ q ≦ Q).

A coordinate system having the origin at the center of the sound field to be estimated is defined as O ₀ . A coordinate system having the origin at the position where the spherical microphone array 850 with the identifier q is arranged (the center of the spherical microphone array 850 with the identifier q) is O _q . Assume that the postures of the coordinate systems, that is, the xyz-axis directions are the same and can be overlapped only by translation. Also, polar coordinates are used for all coordinate systems.

The sound field measuring apparatus 900 of Non-Patent Document 2 uses a spherical wave spectrum vector in the coordinate system O ₀ with the origin of the center of the sound field to be estimated from the collected sound signals recorded using the Q spherical microphone arrays 850. B (k) is obtained.

The position measurement unit 910 measures the position of the arrangement position (center) of the Q spherical microphone arrays 850 arranged in the space in the coordinate system O ₀ (S910). For example, a method of estimating the position from a plurality of camera images based on the principle of triangulation may be used. Position of the spherical microphone array 850 of the identifier q, i.e., the coordinate system _{O q} polar and in the coordinate system _{O 0} of the origin of _{(R q, Θ q, Φ} q) to (1 ≦ q ≦ Q).

The T calculating unit 920 uses the spherical wave spectrum vector A ^(q) (k) (where 1 ≦ q ≦ Q) calculated from the collected sound signals recorded using the Q spherical microphone arrays 850 to determine the spherical wave spectral vector. B mutual transformation matrix T (k) used to calculate the (k), the coordinate system _{O q} of the origin coordinate system _O polar in ₀ of _{(R q, Θ q, Φ} q) is calculated using (S920) . The spherical wave spectrum vector A ^(q) (k) is obtained from the spherical wave spectrum when the polar coordinate display in the coordinate system O _q is used, and the spherical wave spectrum can be calculated by the method described in Non-Patent Document 1. Good. The integrating unit 930 calculates a spherical wave spectrum vector B (k) from the spherical wave spectrum vector A ^(q) (k) (where 1 ≦ q ≦ Q) and the mutual transformation matrix T (k) (S930).

Hereinafter, processing in the T calculation unit 920 and the integration unit 930 will be described in detail.
(Processing in T calculation unit 920)
The polar field of the point x in the coordinate system O ₀ is (R, Θ, Φ), the polar coordinate in the coordinate system O _q is (r, θ, φ), and the sound field at the point x is considered. Let S (x, k) be the sound field at the wave number k of the point x in the coordinate system O ₀ , and S _q (x, k) be the sound field at the wave number k of the point x in the coordinate system O _q . Since the polar coordinate display of the point x in the coordinate system O ₀ is (R, Θ, Φ),

It is expressed. On the other hand, the polar coordinate display of the point x in the coordinate system O _q is (r, θ, φ).

It is expressed. (Expression 5) and (Expression 6) express the same sound field only in different coordinate systems. Therefore, the relationship between the spherical wave spectrum a ⁽⁰⁾ _nm (k) and a ^(q) _νμ (k) is examined.

  From the addition theorem of spherical Bessel functions and spherical harmonics,

Holds true (r = R−Rq). here,

It is. W ₁ and W ₂ are Wigner 3j symbols,

It is. The values of W ₁ and W ₂ can be calculated by the method described in (Reference Non-Patent Document 3).
(Reference Non-Patent Document 3: A. Messiah, “Messiah quantum mechanics 2”, Tokyo Book Co., Ltd., 1972, Appendix C, pp.269-275.)
From (Formula 5), (Formula 6), and (Formula 7),

となる。

It becomes.

(Equation 5) and the expansion order of (Formula 6) as N, a spherical wave spectrum ^a in the coordinate system _{O 0 (0) nm (k} ), the spherical wave spectrum ^a in the coordinate system _{^{O q (q) νμ (k}} ) Spherical wave spectrum vector B (k) and spherical wave spectrum vector A ^(q) (k)

Then, the relationship between B (k) and A ^(q) (k) is described as follows using T ^(q) (k).

Furthermore, since 1 ≦ q ≦ Q,

Is established.

As described above, the process of calculating the matrix T (k) using (Expression 8), (Expression 9-1), and (Expression 9-2) is the process performed by the T calculation unit 920.
(Processing in the integration unit 930)
The integration unit 930 calculates B (k) using the following (Equation 10).

However, T (k) ^H is an adjoint matrix of T (k).

Thushara D. Abhayapala and Darren B. Ward, “Theory and design of high order sound field microphones using spherical microphone array”, in Proc.Acoustics, Speech, and Signal Processing (ICASSP), IEEE International Conference on, IEEE, 2002, vol .II, pp.II-1949. Prasanga N. Samarasinghe, Thushara D. Abhayapala and M.A. Poletti, “3D spatial soundfield recording over large regions”, International Workshop on Acoustics Signal Enhancement 2012, IEEE, 4-6 Sep. 2012, pp.1-4.

Prior art 3 deals with an ideal state where there is no error in spherical wave spectrum vectors A ⁽⁰⁾ (k) to A ^(Q) (k). However, in reality, the microphone elements of the spherical microphone array 850 have an error due to noise, which affects A ⁽⁰⁾ (k) to A ^(Q) (k). As can be seen from (Equation 10), this effect is amplified according to T (k) and transmitted to B (k) when calculating B (k) from A (k). It becomes an error factor of sound field estimation. That is, the estimation accuracy of B (k) is reduced.

  Therefore, the present invention provides a sound field measuring apparatus for estimating a sound field using a spherical wave spectrum vector B (k) whose estimation accuracy is improved by suppressing errors due to noise of microphone elements of a spherical microphone array. The purpose is to do.

In one embodiment of the present invention, Q is an integer greater than or equal to 1, q is an integer greater than or equal to 1 and less than or equal to Q, j _n (·) is an n-th order spherical Bessel function, and Y _nm (·) is a spherical harmonic function of order n and m. , O _q is a polar coordinate system whose origin is the arrangement position of the spherical microphone array with identifier q, and S _q (x, k) is

A sound field at a wave number k of a point x = (r, θ, φ) in the polar coordinate system O _q expressed as _follows : a spherical wave spectrum in the polar coordinate system O _q in which a ^(q) _νμ (k) is determined for each wave number k, By limiting A ^(q) (k) to N as the expansion order of S _q (x, k)

S (x, k) is a polar coordinate system with the origin of the center of the sound field to be estimated as O _0.

A sound field at a wave number k of a point x = (R, Θ, Φ) in the polar coordinate system O ₀ expressed as follows: a spherical wave spectrum in the polar coordinate system O ₀ in which a ⁽⁰⁾ _nm (k) is determined for each wave number k, By limiting B (k) to the expansion order of S (x, k) as N

Is a sound field measuring device that calculates B (k) from A ^(q) (k) using a spherical wave spectrum vector determined as follows, and the arrangement position (R) of the spherical microphone array with the origin and the identifier q in the polar coordinate system O _{0 q} , Θ _q , Φ _q ) to determine the identifier q ′ of the spherical microphone array that minimizes the calculated distance, and the spherical wave spectrum a of the spherical microphone array of the identifier q ′. ^{From (q ′)} _νμ (k), the sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) of the spherical microphone array of the identifier q ′ is calculated as the first sound pressure, and the identifier q ′ For each of the spherical microphone arrays with identifiers 1 to Q except for, the sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) is calculated using the spherical wave spectrum a ^(q) _νμ (k). Calculated as sound pressure, A relative power error calculation unit that calculates a relative power error of the second sound pressure with respect to the first sound pressure, and an identifier of a spherical microphone array that has a predetermined range indicating that the relative power error is small A spherical microphone array identifier selection unit for selecting S, and S is the number of spherical microphone array identifiers selected by the spherical microphone array identifier selection unit (where S ≦ Q), and s is an integer from 1 to Q, and A mutual conversion used to calculate the spherical wave spectrum vector B (k) from the spherical wave spectrum vectors A ^(s) (k) of the S spherical microphone arrays, using the parameters indicating the identifiers of the S spherical microphone arrays. matrix T a (k), the positions of the S spherical microphone array _{(R s, Θ s, Φ} s) using And T calculation unit that exits from the spherical-wave spectral vectors A ^{(s) (k)} and the interconversion matrix T (k), and a integration unit configured to calculate the spherical wave spectrum vector B (k).

  According to the present invention, when calculating the spherical wave spectrum vector B (k), only the spherical wave spectrum of the spherical microphone array with a small error derived from the noise of the microphone element of the spherical microphone array is used, so that the sound field measurement accuracy is obtained. That is, it is possible to improve the estimation accuracy of B (k).

The block diagram which shows the structure of the sound field measuring apparatus 800 of a nonpatent literature 1. FIG. 6 is a flowchart showing the operation of the sound field measuring apparatus 800 of Non-Patent Document 1. The block diagram which shows the structure of the sound field measuring apparatus 900 of a nonpatent literature 2. FIG. 10 is a flowchart showing the operation of the sound field measuring apparatus 900 of Non-Patent Document 2. 1 is a block diagram illustrating a configuration of a sound field measurement apparatus 100 according to a first embodiment. 3 is a flowchart showing the operation of the sound field measuring apparatus 100 according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration of a spherical microphone array selection unit 140 according to the first embodiment. 6 is a flowchart showing the operation of the spherical microphone array selection unit 140 according to the first embodiment. 7 is a detailed flowchart of step S142 which is a part of the operation of the spherical microphone array selection unit 140 according to the first embodiment.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, the same number is attached | subjected to the structure part which has the same function, and duplication description is abbreviate | omitted. Further, in the embodiment of the present invention, as in the method described in Non-Patent Document 1 and the method described in Non-Patent Document 2, a sound field generated by a sound source outside the measurement area is measured, that is, It shall deal with internal problems.

  Hereinafter, the sound field measuring apparatus 100 according to the first embodiment will be described with reference to FIGS. FIG. 5 is a block diagram illustrating a configuration of the sound field measuring apparatus 100 according to the first embodiment. FIG. 6 is a flowchart illustrating the operation of the sound field measuring apparatus 100 according to the first embodiment. As illustrated in FIG. 5, the sound field measurement apparatus 100 according to the first embodiment includes a short-time Fourier transform unit 810, a spherical wave spectrum calculation unit 820, a position measurement unit 910, a T calculation unit 920, and a selection integration unit 130. Including. Further, the selection integration unit 130 includes a spherical microphone array selection unit 140 and an integration unit 930. A spherical microphone array 850 and an omnidirectional microphone 180 for recording the sound field are provided outside the sound field measuring apparatus 900, respectively. It is assumed that there are Q spherical microphone arrays 850, and an identifier q is assigned to identify each of them (Q is an integer of 1 or more, 1 ≦ q ≦ Q). Similarly, there are G omnidirectional microphones 180, and an identifier g is assigned to identify each of them (G is an integer of 1 or more, 1 ≦ g ≦ G). A short-time Fourier transform unit 810 and a spherical wave spectrum calculation unit 820 are provided corresponding to the spherical microphone array 850. Similarly, there is a short-time Fourier transform unit 810 corresponding to the omnidirectional microphone 180.

A coordinate system having the origin at the center of the sound field to be estimated is defined as O ₀ . A coordinate system having the origin at the position where the spherical microphone array 850 with the identifier q is arranged (the center of the spherical microphone array 850 with the identifier q) is O _q . Assume that the postures of the coordinate systems, that is, the xyz-axis directions are the same and can be overlapped only by translation. Also, polar coordinates are used for all coordinate systems. This is the same as the method described in Non-Patent Document 2.

Similar to the method described in Non-Patent Document 2, the sound field measuring apparatus 100 according to the first embodiment uses the center of the sound field to be estimated as the origin from the collected sound signals recorded using the Q spherical microphone arrays 850. The spherical wave spectrum vector B (k) in the coordinate system O ₀ to be calculated is different in that only the spherical wave spectrum vector of the spherical microphone array 850 satisfying a predetermined condition is used for calculating B (k).

The position measurement unit 910 measures the positions of the Q spherical microphone arrays 850 and the G omnidirectional microphones 180 arranged in the space in the coordinate system O ₀ (S910). As described above, for example, a method of estimating a position from a plurality of camera images based on the principle of triangulation may be used. Position of the spherical microphone array 850 of the identifier q, i.e., the coordinate system _{O q} polar and in the coordinate system _{O 0} of the origin of _{(R q, Θ q, Φ} q) to (1 ≦ q ≦ Q). Let polar coordinates in the coordinate system O ₀ of the arrangement position (center) of the omnidirectional microphone 180 with the identifier g be (R _g , Θ _g , Φ _g ) (1 ≦ g ≦ G).

The spherical microphone array selection unit 140 includes an arrangement position (R _q , Θ _q , Φ _q ) of the spherical microphone array 850 having the identifier _q and an arrangement position (R _g , Θ _g , Φ _g ) of the omnidirectional microphone 180 having the identifier g. (1 ≦ q ≦ Q, 1 ≦ g ≦ G) is used to select the spherical microphone array 850 used for calculating the mutual transformation matrix T (k) (S140). The selected spherical microphone array 850 is identified using the identifier. The process of S140 will be described in detail later.

The T calculating unit 920 calculates a spherical wave spectrum vector A ^(s) (k) (where ^s is calculated from a collected sound signal using the selected S (where S ≦ Q) spherical microphone arrays 850). Is an integer greater than or equal to 1 and less than or equal to Q and used as a parameter indicating the identifier of the selected S spherical microphone arrays), the mutual transformation matrix T (k) used for calculating the spherical wave spectrum vector B (k) the coordinate system _{O s} of the origin coordinate system _O polar in ₀ of _{(R s, Θ s, Φ} s) is calculated using (S920). The spherical wave spectrum vector A ^(s) (k) is obtained from the spherical wave spectrum when the polar coordinate display in the coordinate system O _s is used, and the spherical wave spectrum can be calculated by the method described in Non-Patent Document 1. Good. The integrating unit 930 calculates a spherical wave spectrum vector B (k) from the spherical wave spectrum vector A ^(s) (k) and the mutual transformation matrix T (k) (S930).

  Hereinafter, the spherical microphone array selection unit 140 will be described with reference to FIGS. FIG. 7 is a block diagram illustrating a configuration of the spherical microphone array selection unit 140. FIG. 8 is a flowchart showing the operation of the spherical microphone array selection unit 140. FIG. 9 is a diagram showing a detailed processing flow of S142 which is a part of the operation of the spherical microphone array selection unit 140 shown in FIG. As shown in FIG. 7, the spherical microphone array selection unit 140 includes a closest microphone determination unit 141, a relative power error calculation unit 142, and a spherical microphone array identifier selection unit 143.

The closest microphone determining unit 141 arranges the arrangement position (R _q , Θ _q , Φ _q ) of the spherical microphone array 850 with the identifier _q and the arrangement position (R _g , Θ _g , Φ _g ) of the omnidirectional microphone 180 with the identifier g. (1 ≦ q ≦ Q, 1 ≦ g ≦ G) is used to determine the spherical microphone array 850 or the omnidirectional microphone 180 closest to the origin of the coordinate system O ₀ that is the center of the sound field to be estimated ( S141). Specifically, the identifier q or g of the smallest one of R _q and R _g (1 ≦ q ≦ Q, 1 ≦ g ≦ G) may be selected.

The relative power error calculation unit 142 calculates the relative power error by a method according to whether the microphone closest to the origin of the coordinate system O ₀ is the spherical microphone array 850 or the omnidirectional microphone 180 (S142). When the closest is spherical microphone array 850 (identifier is q ′) (that is, YES in S1421), first, the arrangement position (R _{q ′} , Θ _q ) of spherical microphone array 850 with identifier q ′ is used. The sound pressure at _' , Φ _q' ) is calculated (S1422a). This is the first sound pressure. The first sound pressure can be calculated as a spherical wave spectrum a ^{(q ′)} ₀₀ (k). Next, with respect to the spherical microphone array 850 of the identifiers 1 to Q excluding the identifier q ′, the arrangement position (R _{q ′} ) of the spherical microphone array 850 of the identifier q ′ is used using the spherical wave spectrum a ^(q) _nm (k). , Θ _{q ′} , Φ _{q ′} ) is estimated and calculated as the second sound pressure (S1423a). For the second sound pressure a ^ ^{(q ′)} _q (k), after calculating the polar coordinates of the arrangement position of the spherical microphone array 850 of the identifier q ′ in the coordinate system O _q , the polar coordinates are substituted into (Expression 6). This can be calculated. Finally, the relative power error of a ^ ^{(q ′)} _q (k) with respect to a ^{(q ′)} ₀₀ (k) is calculated (S1424a). That is, (Q-1) relative power errors are calculated. The relative power error can be calculated as | a ^{(q ′)} ₀₀ (k) −a ^ ^{(q ′)} _q (k) | / | a ^{(q ′)} ₀₀ (k) |.

On the other hand, when the closest one is omnidirectional microphone 180 (identifier is g ′) (that is, NO in S1421), first, the arrangement position of omnidirectional microphone 180 of identifier g ′ (R _{g ', Θ g',} calculates the sound pressure at Φ _{g ')} (S1422b). This is the third sound pressure. The third sound pressure p _{g ′} (k) is obtained as a frequency f = kc / 2π from a frequency domain signal obtained by performing a short-time Fourier transform on the collected sound signal recorded by the omnidirectional microphone 180 having the identifier g ′. Can be calculated. Next, with respect to the spherical microphone array 850 with the identifiers 1 to Q, using the spherical wave spectrum a ^(q) _nm (k), the arrangement positions (R _{g ′} , Θ _{g ′} , The sound pressure at Φ _{g ′} ) is estimated and calculated as the fourth sound pressure (S1423b). The fourth sound pressure a ^ ^{(g ′)} _q (k) can be calculated by a method similar to the method in S1423a. Finally, the relative power error of a ^ ^{(g ′)} _q (k) with respect to p _{g ′} (k) is calculated (S1424b). That is, Q relative power errors are calculated. The relative power error can be calculated by a method similar to the method in S1424a.

  Note that the processing in the short-time Fourier transform unit 810 that calculates the frequency domain signal from the collected sound signal recorded by the omnidirectional microphone 180 by the short-time Fourier transform is unnecessary when the closest one is the spherical microphone array 850. The processing may be delayed until the determination processing of S1421 is executed.

  The spherical microphone array identifier selection unit 143 determines the spherical microphone array 850 that falls within a predetermined range indicating that the relative power error calculated in S142 is small as a spherical microphone array used for calculating the mutual transformation matrix T (k) (S143). ). For example, the predetermined range may be equal to or less than a preset threshold value or may be smaller than a preset threshold value. Moreover, the said threshold value is good to set it as 0.2-0.3.

The arrangement positions (R _q , Θ _q , Φ _q ) and (R _g , Θ _g , Φ _g ) (1 ≦ q ≦ Q, 1 ≦ g ≦ G) of the spherical microphone array 850 and the omnidirectional microphone 180 are determined. If known in advance, the sound field measuring apparatus 100 can be configured without the position measuring unit 910.

  Further, the sound field measuring apparatus 100 may be configured without the omnidirectional microphone 180. In this case, the processing flow of S142 illustrated in FIG. 9 does not require the determination processing of S1421, and thus only performs the processing of S1422a, S1423a, and S1424a.

From the spherical wave spectrum vector A ^(s) (k) and the mutual transformation matrix T (k), the spherical wave spectrum vector B (k) is calculated using (Equation 10). The estimation of the sound field using B (k) calculated in this way is basically extrapolation, and the extrapolation error is influenced by the relative positional relationship of the spherical microphone array and the like. In the present invention, the validity of this extrapolation is checked, and B (k) is calculated by excluding spherical microphone arrays that cannot be regarded as valid, that is, those whose relative power error is not within a predetermined range. As a result, B (k) can finally be calculated better.
<Supplementary note>
The apparatus of the present invention includes, for example, a single hardware entity as an input unit to which a keyboard or the like can be connected, an output unit to which a liquid crystal display or the like can be connected, and a communication device (for example, a communication cable) capable of communicating outside the hardware entity. Can be connected to a communication unit, a CPU (Central Processing Unit, may include a cache memory or a register), a RAM or ROM that is a memory, an external storage device that is a hard disk, and an input unit, an output unit, or a communication unit thereof , A CPU, a RAM, a ROM, and a bus connected so that data can be exchanged between the external storage devices. If necessary, the hardware entity may be provided with a device (drive) that can read and write a recording medium such as a CD-ROM. A physical entity having such hardware resources includes a general-purpose computer.

  The external storage device of the hardware entity stores a program necessary for realizing the above functions and data necessary for processing the program (not limited to the external storage device, for example, reading a program) It may be stored in a ROM that is a dedicated storage device). Data obtained by the processing of these programs is appropriately stored in a RAM or an external storage device.

  In the hardware entity, each program stored in an external storage device (or ROM or the like) and data necessary for processing each program are read into a memory as necessary, and are interpreted and executed by a CPU as appropriate. . As a result, the CPU realizes a predetermined function (respective component requirements expressed as the above-described unit, unit, etc.).

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention. In addition, the processing described in the above embodiment may be executed not only in time series according to the order of description but also in parallel or individually as required by the processing capability of the apparatus that executes the processing. .

  As described above, when the processing functions in the hardware entity (the apparatus of the present invention) described in the above embodiments are realized by a computer, the processing contents of the functions that the hardware entity should have are described by a program. Then, by executing this program on a computer, the processing functions in the hardware entity are realized on the computer.

  The program describing the processing contents can be recorded on a computer-readable recording medium. As the computer-readable recording medium, for example, any recording medium such as a magnetic recording device, an optical disk, a magneto-optical recording medium, and a semiconductor memory may be used. Specifically, for example, as a magnetic recording device, a hard disk device, a flexible disk, a magnetic tape or the like, and as an optical disk, a DVD (Digital Versatile Disc), a DVD-RAM (Random Access Memory), a CD-ROM (Compact Disc Read Only). Memory), CD-R (Recordable) / RW (ReWritable), etc., magneto-optical recording medium, MO (Magneto-Optical disc), etc., semiconductor memory, EEP-ROM (Electronically Erasable and Programmable-Read Only Memory), etc. Can be used.

  The program is distributed by selling, transferring, or lending a portable recording medium such as a DVD or CD-ROM in which the program is recorded. Furthermore, the program may be distributed by storing the program in a storage device of the server computer and transferring the program from the server computer to another computer via a network.

  A computer that executes such a program first stores, for example, a program recorded on a portable recording medium or a program transferred from a server computer in its own storage device. When executing the process, the computer reads a program stored in its own recording medium and executes a process according to the read program. As another execution form of the program, the computer may directly read the program from a portable recording medium and execute processing according to the program, and the program is transferred from the server computer to the computer. Each time, the processing according to the received program may be executed sequentially. Also, the program is not transferred from the server computer to the computer, and the above-described processing is executed by a so-called ASP (Application Service Provider) type service that realizes the processing function only by the execution instruction and result acquisition. It is good. Note that the program in this embodiment includes information that is used for processing by an electronic computer and that conforms to the program (data that is not a direct command to the computer but has a property that defines the processing of the computer).

  In this embodiment, a hardware entity is configured by executing a predetermined program on a computer. However, at least a part of these processing contents may be realized by hardware.

Claims (5)

Q is an integer greater than or equal to 1, q is an integer greater than or equal to 1 and less than or equal to Q, j _n (·) is an n-order spherical Bessel function, Y _nm (·) is a spherical harmonic function of order n, m, and O _q is an identifier q A polar coordinate system having the origin of the arrangement position of the spherical microphone array, S _q (x, k)

A sound field at a wave number k of a point x = (r, θ, φ) in the polar coordinate system O _q expressed as _follows : a spherical wave spectrum in the polar coordinate system O _q in which a ^(q) _νμ (k) is determined for each wave number k, By limiting A ^(q) (k) to N as the expansion order of S _q (x, k)

S (x, k) is a polar coordinate system with the origin of the center of the sound field to be estimated as O _0.

A sound field at a wave number k of a point x = (R, Θ, Φ) in the polar coordinate system O ₀ expressed as follows: a spherical wave spectrum in the polar coordinate system O ₀ in which a ⁽⁰⁾ _nm (k) is determined for each wave number k, By limiting B (k) to the expansion order of S (x, k) as N

Spherical wave spectrum vector determined as
A sound field measuring device for calculating B (k) from A ^(q) (k),
The distance between the origin and the position (R _q , Θ _q , Φ _q ) of the spherical microphone array with the identifier q in the polar coordinate system O ₀ is obtained, and the identifier q ′ of the spherical microphone array with the smallest obtained distance is determined. A microphone contact unit,
The sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) of the spherical microphone array with the identifier q ′ is determined from the spherical wave spectrum a ^{(q ′)} _νμ (k) of the spherical microphone array with the identifier q ′. The arrangement position (R _{q ′} , Θ _q ) is calculated using the spherical wave spectrum a ^(q) _νμ (k) for each of the spherical microphone arrays with identifiers 1 to Q excluding the identifier q ′, calculated as the first sound pressure. _' , Φ _q' ) as a second sound pressure, and a relative power error calculation unit that calculates a relative power error of the second sound pressure with respect to the first sound pressure as a relative power error;
A spherical microphone array identifier selection unit for selecting an identifier of a spherical microphone array that falls within a predetermined range indicating that the relative power error is small;
S is the number of spherical microphone array identifiers selected by the spherical microphone array identifier selection unit (where S ≦ Q), s is an integer from 1 to Q, and indicates the identifiers of the S spherical microphone arrays age,
The mutual conversion matrix T (k) used to calculate the spherical wave spectrum vector B (k) from the spherical wave spectrum vectors A ^(s) (k) of the S spherical microphone arrays is represented by the S spherical microphones. A T calculator for calculating using the array arrangement position (R _s , Θ _s , Φ _s );
A sound field measuring apparatus including an integrating unit that calculates the spherical wave spectrum vector B (k) from the spherical wave spectrum vector A ^(s) (k) and the mutual transformation matrix T (k). Q is an integer greater than or equal to 1, q is an integer greater than or equal to 1 and less than or equal to Q, j _n (·) is an n-order spherical Bessel function, Y _nm (·) is a spherical harmonic function of order n, m, and O _q is an identifier q A polar coordinate system having the origin of the arrangement position of the spherical microphone array, S _q (x, k)

A sound field at a wave number k of a point x = (r, θ, φ) in the polar coordinate system O _q expressed as _follows : a spherical wave spectrum in the polar coordinate system O _q in which a ^(q) _νμ (k) is determined for each wave number k, By limiting A ^(q) (k) to N as the expansion order of S _q (x, k)

S (x, k) is a polar coordinate system with the origin of the center of the sound field to be estimated as O _0.

A sound field at a wave number k of a point x = (R, Θ, Φ) in the polar coordinate system O ₀ expressed as follows: a spherical wave spectrum in the polar coordinate system O ₀ in which a ⁽⁰⁾ _nm (k) is determined for each wave number k, By limiting B (k) to the expansion order of S (x, k) as N

Spherical wave spectrum vector determined as
A sound field measuring device for calculating B (k) from A ^(q) (k),
Position of the spherical microphone array origin identifier q in the polar coordinate system _{O 0 (R q, Θ q} , Φ q) distance and location of omni-directional microphones of origin identifier g of the polar coordinate system O ₀ of (R _g , Θ _g , Φ _g ) (where 1 ≦ g ≦ G, G is an integer of 1 or more), and the identifier q ′ of the spherical microphone array or the identifier of the omnidirectional microphone that minimizes the calculated distance a closest microphone determining unit for determining g ′;
When the identifier determined by the closest microphone determination unit is that of the spherical microphone array, the spherical surface of the identifier q ′ is obtained from the spherical wave spectrum a ^{(q ′)} _νμ (k) of the spherical microphone array of the identifier q ′. The sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) of the microphone array is calculated as the first sound pressure, and the spherical wave for each of the spherical microphone arrays of identifiers 1 to Q excluding the identifier q ′. A sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) is calculated as a second sound pressure using the spectrum a ^(q) _νμ (k), and the first sound pressure relative to the first sound pressure is calculated. The relative power error of the sound pressure of 2 is calculated as the relative power error, and when the identifier determined by the closest microphone determination unit is that of the omnidirectional microphone, recorded by the omnidirectional microphone of the identifier g ′ did 'Location of omni-directional microphones (R _g' from the sound signal the identifier _{g, Θ g ', Φ g} ') the sound pressure at calculated as a third sound pressure, an identifier 1~Q spherical microphone array Using the spherical wave spectrum a ^(q) _νμ (k) for each, the sound pressure at the arrangement position (R _{g ′} , Θ _{g ′} , Φ _{g ′} ) is calculated as a fourth sound pressure, and the third sound is calculated. A relative power error calculation unit that calculates a relative power error of the fourth sound pressure with respect to a pressure as a relative power error;
A spherical microphone array identifier selection unit for selecting an identifier of a spherical microphone array that falls within a predetermined range indicating that the relative power error is small;
S is the number of spherical microphone array identifiers selected by the spherical microphone array identifier selection unit (where S ≦ Q), s is an integer from 1 to Q, and indicates the identifiers of the S spherical microphone arrays age,
The mutual conversion matrix T (k) used to calculate the spherical wave spectrum vector B (k) from the spherical wave spectrum vectors A ^(s) (k) of the S spherical microphone arrays is represented by the S spherical microphones. A T calculator for calculating using the array arrangement position (R _s , Θ _s , Φ _s );
A sound field measuring apparatus including an integrating unit that calculates the spherical wave spectrum vector B (k) from the spherical wave spectrum vector A ^(s) (k) and the mutual transformation matrix T (k). Q is an integer greater than or equal to 1, q is an integer greater than or equal to 1 and less than or equal to Q, j _n (·) is an n-order spherical Bessel function, Y _nm (·) is a spherical harmonic function of order n, m, and O _q is an identifier q A polar coordinate system having the origin of the arrangement position of the spherical microphone array, S _q (x, k)

A sound field at a wave number k of a point x = (r, θ, φ) in the polar coordinate system O _q expressed as _follows : a spherical wave spectrum in the polar coordinate system O _q in which a ^(q) _νμ (k) is determined for each wave number k, By limiting A ^(q) (k) to N as the expansion order of S _q (x, k)

S (x, k) is a polar coordinate system with the origin of the center of the sound field to be estimated as O _0.

A sound field at a wave number k of a point x = (R, Θ, Φ) in the polar coordinate system O ₀ expressed as follows: a spherical wave spectrum in the polar coordinate system O ₀ in which a ⁽⁰⁾ _nm (k) is determined for each wave number k, By limiting B (k) to the expansion order of S (x, k) as N

Spherical wave spectrum vector determined as
A sound field measuring method for calculating B (k) from A ^(q) (k),
The distance between the origin and the position (R _q , Θ _q , Φ _q ) of the spherical microphone array with the identifier q in the polar coordinate system O ₀ is obtained, and the identifier q ′ of the spherical microphone array with the smallest obtained distance is determined. The microphone contact step,
The sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) of the spherical microphone array with the identifier q ′ is determined from the spherical wave spectrum a ^{(q ′)} _νμ (k) of the spherical microphone array with the identifier q ′. The arrangement position (R _{q ′} , Θ _q ) is calculated using the spherical wave spectrum a ^(q) _νμ (k) for each of the spherical microphone arrays with identifiers 1 to Q excluding the identifier q ′, calculated as the first sound pressure. A relative power error calculating step of calculating a sound pressure at _' , Φ _q' ) as a second sound pressure, and calculating a relative power error of the second sound pressure with respect to the first sound pressure as a relative power error;
A spherical microphone array identifier selection step of selecting an identifier of a spherical microphone array that falls within a predetermined range indicating that the relative power error is small;
S is the number of identifiers of the spherical microphone array selected in the spherical microphone array identifier selection step (where S ≦ Q), and s is an integer between 1 and Q, indicating the identifiers of the S spherical microphone arrays. Parameter,
The mutual conversion matrix T (k) used to calculate the spherical wave spectrum vector B (k) from the spherical wave spectrum vectors A ^(s) (k) of the S spherical microphone arrays is represented by the S spherical microphones. A T calculating step for calculating using the array arrangement position (R _s , Θ _s , Φ _s );
A sound field measuring method including an integrating step of calculating the spherical wave spectrum vector B (k) from the spherical wave spectrum vector A ^(s) (k) and the mutual transformation matrix T (k). Q is an integer greater than or equal to 1, q is an integer greater than or equal to 1 and less than or equal to Q, j _n (·) is an n-order spherical Bessel function, Y _nm (·) is a spherical harmonic function of order n, m, and O _q is an identifier q A polar coordinate system having the origin of the arrangement position of the spherical microphone array, S _q (x, k)

A sound field at a wave number k of a point x = (r, θ, φ) in the polar coordinate system O _q expressed as _follows : a spherical wave spectrum in the polar coordinate system O _q in which a ^(q) _νμ (k) is determined for each wave number k, By limiting A ^(q) (k) to N as the expansion order of S _q (x, k)

S (x, k) is a polar coordinate system with the origin of the center of the sound field to be estimated as O _0.

A sound field at a wave number k of a point x = (R, Θ, Φ) in the polar coordinate system O ₀ expressed as follows: a spherical wave spectrum in the polar coordinate system O ₀ in which a ⁽⁰⁾ _nm (k) is determined for each wave number k, By limiting B (k) to the expansion order of S (x, k) as N

Spherical wave spectrum vector determined as
A sound field measuring method for calculating B (k) from A ^(q) (k),
Position of the spherical microphone array origin identifier q in the polar coordinate system _{O 0 (R q, Θ q} , Φ q) distance and location of omni-directional microphones of origin identifier g of the polar coordinate system O ₀ of (R _g , Θ _g , Φ _g ) (where 1 ≦ g ≦ G, G is an integer of 1 or more), and the identifier q ′ of the spherical microphone array or the identifier of the omnidirectional microphone that minimizes the calculated distance a closest microphone determining step for determining g ′;
When the identifier determined in the closest microphone determination step is that of a spherical microphone array, the spherical surface of the identifier q ′ is obtained from the spherical wave spectrum a ^{(q ′)} _νμ (k) of the spherical microphone array of the identifier q ′. The sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) of the microphone array is calculated as the first sound pressure, and the spherical wave for each of the spherical microphone arrays of identifiers 1 to Q excluding the identifier q ′. A sound pressure at the arrangement position (R _{q ′} , Θ _{q ′} , Φ _{q ′} ) is calculated as a second sound pressure using the spectrum a ^(q) _νμ (k), and the first sound pressure relative to the first sound pressure is calculated. 2 is calculated as a relative power error, and when the identifier determined in the closest microphone determination step is that of an omnidirectional microphone, the omnidirectional microphone of the identifier g ′ is calculated. From in From the collected sound signal the 'positions of the omnidirectional microphones (R _g' identifier _{g, Θ g ', Φ g} ') the sound pressure at calculated as a third sound pressure, the identifier 1~Q For each of the spherical microphone arrays, the sound pressure at the arrangement position (R _{g ′} , Θ _{g ′} , Φ _{g ′} ) is calculated as the fourth sound pressure using the spherical wave spectrum a ^(q) _νμ (k), A relative power error calculation step of calculating a relative power error of the fourth sound pressure with respect to a third sound pressure as a relative power error;
A spherical microphone array identifier selection step of selecting an identifier of a spherical microphone array that falls within a predetermined range indicating that the relative power error is small;
S is the number of identifiers of the spherical microphone array selected in the spherical microphone array identifier selection step (where S ≦ Q), and s is an integer between 1 and Q, indicating the identifiers of the S spherical microphone arrays. Parameter,
The mutual conversion matrix T (k) used to calculate the spherical wave spectrum vector B (k) from the spherical wave spectrum vectors A ^(s) (k) of the S spherical microphone arrays is represented by the S spherical microphones. A T calculating step for calculating using the array arrangement position (R _s , Θ _s , Φ _s );
A sound field measuring method including an integrating step of calculating the spherical wave spectrum vector B (k) from the spherical wave spectrum vector A ^(s) (k) and the mutual transformation matrix T (k).   A program for causing a computer to function as the sound field measuring device according to claim 1.

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