Sound source probing apparatus, sound source probing method, and storage medium storing program therefor

1. A sound source probing apparatus that probes a direction of a sound source, comprising:

storage; and

processing circuitry that, in operation, performs operations including

determining a first correlation matrix that is a correlation matrix of acoustic signals acquired as observation signals by a microphone array including two or more microphones disposed apart from each other,

determining, by learning, weights such that a linear sum of a plurality of second correlation matrices multiplied by the respective weights is equal to the first correlation matrix where the plurality of second correlation matrices are correlation matrices, which are determined for respective directions determined based on an array arrangement of the microphone array and which are stored in advance in the storage, and

determining, using the determined weights, a spatial spectrum of the observation signal indicating sound pressure intensities in the respective directions.

2. The sound source probing apparatus according to claim 1 ,

wherein the operations further include

selecting one first element from elements of the first correlation matrix and also selecting one second element from elements of each of the second correlation matrices such that each second element is at a matrix element position corresponding to a matrix element position of the first element, and

sequentially changing the first element and the second elements by changing the matrix element position at which the first and second elements are selected, and

wherein the determining of the weights includes

updating the weights from first values to second values that allow a linear sum of the second elements multiplied by the respective second values of the weights to be equal to the first element,

updating the weights from the second values to third values that allow a linear sum of next-selected second elements multiplied by the respective third values of the weights to be equal to a next-selected first element, and

further repeating the updating of the values of the weights each time the first element and the second elements are changed thereby determining the weights.

3. The sound source probing apparatus according to claim 2 ,

wherein in the selecting, the first element and the second elements are selected only from either one of two groups of elements of respective correlation matrices including the first correlation matrix and the second correlation matrices, the two groups of elements of each correlation matrix being defined such that the correlation matrix is divided into the two groups by a boundary defined by diagonal elements such that each group includes a plurality of elements but does not include the diagonal elements.

4. The sound source probing apparatus according to claim 1 ,

wherein in the determining of the weights, the weights are determined based on the second correlation matrix and an error between the linear sum and the first correlation matrix using an LMS (Least Mean Square) algorithm or ICA (Independent Component Analysis).

5. The sound source probing apparatus according to claim 1 ,

wherein the determining of the weights includes

holding the weights,

determining a linear sum of the products of the second correlation matrices and the respective held weights,

determining an error defined by the difference between the linear sum and the first correlation matrix,

determining weight change amounts from the error and the products of the second correlation matrices and the weights, and

updating the weights by addling the weight change amounts to the respective held weights.

6. The sound source probing apparatus according to claim 5 ,

wherein in the determining of the weights, the weight change amounts may be determined from the error and the second correlation matrices using an LMS algorithm or ICA.

7. The sound source probing apparatus according to claim 5 ,

wherein the determining of the weights may further include adding nonlinearity to the error using a predetermined nonlinear function, and

in the determining of the update amounts, the weight change amounts are determined from the error added with the nonlinearity and the second correlation matrices.

8. A method of probing a direction of a sound source, comprising:

determining a first correlation matrix that is a correlation matrix of acoustic signals acquired as observation signals by a microphone array including two or more microphones disposed apart from each other;

determining, by learning, weights such that a linear sum of a plurality of second correlation matrices multiplied by the respective weights is equal to the first correlation matrix where the plurality of second correlation matrices are correlation matrices, which are determined for respective directions determined based on an array arrangement of the microphone array and which are stored in advance in storage, and

determining, using the determined weights, a spatial spectrum of the observation signal indicating sound pressure intensities in the respective directions.

9. A computer-readable non-transitory storage medium storing a program for causing a computer to execute a method of probing a direction of a sound source, the program, when executed by the computer, causing the computer to execute the method including

determining a first correlation matrix that is a correlation matrix of acoustic signals acquired as observation signals by a microphone array including two or more microphones disposed apart from each other,

determining, by learning, weights such that a linear sum of a plurality of second correlation matrices multiplied by the respective weights is equal to the first correlation matrix where the plurality of second correlation matrices are correlation matrices, which are determined for respective directions determined based on an array arrangement of the microphone array and which are stored in advance in storage, and

determining, using the determined weights, a spatial spectrum of the observation signal indicating sound pressure intensities in the respective directions.