Correlation function generation apparatus, correlation function generation method, correlation function generation program, and wave source direction estimation apparatus
A correlation function having a clear peak is generated even in an environment in which an ambient noise level is high. A correlation function generation apparatus ( 100 ) includes a plurality of input signal obtaining units ( 101 ), a changing unit ( 102 ), a cross-spectrum calculator ( 103 ), a variance calculator ( 104 ), and a correlation function calculator ( 105 ). The input signal obtaining unit ( 101 ) obtains a wave generated by a wave source as an input signal. The transformer ( 102 ) obtains a plurality of frequency domain signals by transforming a plurality of input signals obtained by the plurality of input signal obtaining units. The cross-spectrum calculator ( 103 ) calculates a cross-spectrum based on the plurality of frequency domain signals. The variance calculator ( 104 ) calculates the variance of the cross-spectrum. The correlation function calculator ( 105 ) calculates and generates a correlation function based on the cross-spectrum and the variance.
1. A correlation function generation apparatus comprising:
a memory configured to store instructions; and
a processor configured to execute the instructions to:
obtain a plurality of input signals associated with ambient noise and a target sound source, the plurality of input signals detected by at least two microphones;
obtain a plurality of frequency domain signals by transforming the plurality of input signals;
calculate a cross-spectrum based on said plurality of frequency domain signals;
obtain a circular variance of said cross-spectrum as a variance of a phase of said cross-spectrum; and
generate a correlation function to be used for estimating a direction of said target sound source, based on said cross-spectrum weighted by a weight calculated from said obtained circular variance, wherein the weight is inversely proportional to the obtained circular variance.
2. The correlation function generation apparatus according to claim 1 , wherein the processor is further configured to execute the instructions to calculate an average cross-spectrum by averaging said cross-spectra, and
calculate said circular variance based on said average cross-spectrum.
3. The correlation function generation apparatus according to claim 1 , wherein
the processor is configured to execute the instructions to calculate one correlation function by generating a plurality of cross-spectra-by-frequencies based on said circulate variance and said cross-spectrum, and
integrating said plurality of cross-spectra-by-frequencies.
4. The correlation function generation apparatus according to claim 3 , wherein
the processor is configured to execute the instructions to calculate said one correlation function by obtaining a plurality of correlation-functions-by-frequencies by calculating inverse transform of said plurality of first cross-spectra-by-frequencies, and
integrating said plurality of correlation-functions-by-frequencies that have been calculated inverse transform.
5. The correlation function generation apparatus according to claim 3 , wherein
the processor is configured to execute the instructions to generate said plurality of cross-spectra-by-frequencies by generating a kernel function spectrum based on said variance, and
multiplying said cross-spectra-by-frequencies by said kernel function spectrum.
6. The correlation function generation apparatus according to claim 3 , wherein
the processor is configured to execute the instructions to generate said plurality of cross-spectra-by-frequencies by selecting one of a plurality of kernel function spectra stored in a kernel function spectrum storage, based on said circulate variance, and
multiplying said cross-spectra-by-frequencies by said selected kernel function spectrum.
7. The correlation function generation apparatus according to claim 3 , wherein the processor is configured to execute the instructions to calculate the one correlation function by obtaining one integrated cross-spectrum by integrating said plurality of cross-spectra-by-frequencies, and
calculating inverse transform of said one integrated cross-spectrum.
8. The correlation function generation apparatus according to claim 1 , wherein the processor is further configured to execute the instructions to estimate a direction of said target sound source based on the correlation function.
9. A correlation function generation method comprising:
obtaining a plurality of input signals associated with ambient noise and a target sound source, the plurality of input signals detected by at least two microphones;
obtaining a plurality of frequency domain signals by transforming the plurality of input signals;
calculating a cross-spectrum based on said plurality of frequency domain signals;
obtain a circular variance of said cross-spectrum as a variance of a phase of said cross-spectrum; and
generate a correlation function to be used for estimating a direction of said target sound source, based on said cross-spectrum weighted by a weight calculated from said obtained circular variance, wherein the weight is inversely proportional to the obtained circular variance.
10. The correlation function generation method of claim 9 , further comprising:
estimating a direction of said target sound source based on the correlation function.
11. A non-transitory computer readable storage medium storing a correlation function generation program for causing a computer to execute a method, the method comprising:
obtaining a plurality of input signals associated with ambient noise and a target sound source, the plurality of input signals detected by at least two microphones;
obtaining a plurality of frequency domain signals by transforming the plurality of input signals;
calculating a cross-spectrum based on said plurality of frequency domain signals;
obtain a circular variance of said cross-spectrum as a variance of a phase of said cross-spectrum; and
generate a correlation function to be used for estimating a direction of said target sound source, based on said cross-spectrum weighted by a weight calculated from said obtained circular variance, wherein the weight is inversely proportional to the obtained circular variance.
12. The non-transitory computer readable storage medium of claim 11 , further comprising:
estimating a direction of said target sound source based on the correlation function.