Noise suppressing apparatus, speech recognition apparatus, and noise suppressing method

A speech recognition apparatus that suppresses noise included in a sound signal and performs speech recognition processing on a sound signal in which the noise has been suppressed, the speech recognition apparatus comprising:

• a memory;
• and
• a processor configured to be connected to the memory and to perform processing of suppressing the noise included in the sound signal, wherein
• the processing of suppressing the noise includes:
• calculating a phase difference on the basis of frequency spectra of a first sound signal and a second sound signal obtained by picking up a pickup target sound using a microphone array;
• calculating a first sound arrival rate on the basis of a first phase difference area and the phase difference and calculating a second sound arrival rate on the basis of a second phase difference area and the phase difference, wherein the first phase difference area is set on the basis of a direction of arrival of the pickup target sound which arrives at the microphone array, and the second phase difference area is different from the first phase difference area;
• calculating a dissimilarity that represents a level of difference between the first sound arrival rate and the second sound arrival rate;
• determining whether the pickup target sound is included in the first sound signal on the basis of the dissimilarity;
• determining a suppression coefficient to be applied to the frequency spectrum with respect to the first sound signal, on the basis of a result of the determination of whether the pickup target sound is included and on the basis of the phase difference;
• applying the determined suppression coefficient to the frequency spectrum;
• and
• transforming the frequency spectrum to which the suppression coefficient has been applied into a sound signal.

A noise suppressing method for suppressing noise included in a sound signal, the noise suppressing method comprising:

• calculating, by a computer, a phase difference on the basis of frequency spectra of a first sound signal and a second sound signal obtained by picking up a pickup target sound using a microphone array;
• calculating, by the computer, a first sound arrival rate on the basis of a first phase difference area and the phase difference and calculating, by the computer, a second sound arrival rate on the basis of a second phase difference area and the phase difference, wherein the first phase difference area is set on the basis of a direction of arrival of the pickup target sound which arrives at the microphone array, and the second phase difference area is different from the first phase difference area;
• calculating, by the computer, a dissimilarity that represents a level of difference between the first sound arrival rate and the second sound arrival rate;
• determining, by the computer, whether the pickup target sound is included in the first sound signal on the basis of the dissimilarity;
• and
• determining, by the computer, a suppression coefficient to be applied to the frequency spectrum with respect to the first sound signal, on the basis of a result of the determination of whether the pickup target sound is included and on the basis of the phase difference.