Sound pickup device and sound pickup method

1. A sound pickup device comprising:

a calculator that:

obtains a first sound pickup signal to be generated from a first sound signal output by a first microphone and a second sound pickup signal to be generated from a second sound signal output by a second microphone;

converts the first sound pickup signal and the second sound pickup signal into a first frequency signal and a second frequency signal;

calculates a coherence between the first frequency signal and the second frequency signal; and

calculates a ratio of a frequency component of which the calculated coherence exceeds a first threshold value with respect to all frequency components; and

a level controller that controls a level of the first sound pickup signal or the second sound pickup signal according to the calculated ratio.

2. The sound pickup device according to claim 1 , further comprising:

the first microphone; and

the second microphone.

3. The sound pickup device according to claim 1 , wherein the level controller determines whether or not the calculated coherence exceeds the first threshold value for each frequency component, obtains the calculated ratio by totaling the number of frequency components that exceeds the first threshold value with respect to the all frequency components.

4. The sound pickup device according to claim 1 , wherein the level controller includes a directivity former that generates the first sound pickup signal and the second sound pickup signal from the first sound signal output by the first microphone and the second sound signal output by the second microphone.

5. The sound pickup device according to claim 4 , wherein:

the first microphone and the second microphone are directional microphones, and

the directivity former generates the first sound pickup signal having directivity, and the second sound pickup signal having non-directivity, from the first and second signals output by the first microphone and the second microphone.

6. The sound pickup device according to claim 4 , wherein the directivity former generates the first sound pickup signal or the second sound pickup signal by obtaining a sum of delays of the first and second sound signals output by the first microphone and the second microphone.

7. The sound pickup device according to claim 1 , wherein the level controller estimates a noise component, and reduces the estimated noise component from the first sound pickup signal or the second sound pickup signal to control the level thereof.

8. The sound pickup device according to claim 7 , wherein the level controller, according to the calculated ratio, turns on or off the noise component reduction.

9. The sound pickup device according to claim 1 , wherein the level controller includes a comb filter that reduces a harmonic component based on sound.

10. The sound pickup device according to claim 9 , wherein the level controller, according to the calculated ratio, turns on or off processing by the comb filter.

11. The sound pickup device according to claim 1 , wherein the level controller includes a gain controller that controls a gain of the first sound pickup signal or the second sound pickup signal.

12. The sound pickup device according to claim 11 , wherein the level controller attenuates the gain according to the calculated ratio in a case where the calculated ratio is less than a second threshold value.

13. The sound pickup device according to claim 12 , wherein the second threshold value is determined based on the calculated ratio calculated within a predetermined time.

14. The sound pickup device according to claim 11 , wherein the level controller sets the gain as a minimum gain in a case where the calculated ratio is less than a second threshold value.

15. A sound pickup method comprising:

obtaining a correlation between a first sound pickup signal to be generated from a first sound signal output by a first microphone and a second sound pickup signal to be generated from a second sound signal output by a second microphone; and

converting the first sound pickup signal and the second sound pickup signal into a first frequency signal and a second frequency signal;

calculating a coherence between the first frequency signal and the second frequency signal;

calculating a ratio of a frequency component of which the calculated coherence exceeds a first threshold value with respect to all frequency components; and

controlling a level of the first sound pickup signal or the second sound pickup signal according to the calculated ratio.

16. The sound pickup method according to claim 15 , further comprising determining whether or not the calculated coherence exceeds the first threshold value for each frequency component, obtaining the calculated ratio by totaling the number of frequency components that exceeds the first threshold value with respect to the all frequency components.

17. The sound pickup method according to claim 15 , further comprising generating the first sound pickup signal and the second sound pickup signal from the first sound signal output by the first microphone and the second sound signal output by the second microphone.

18. The sound pickup method according to claim 17 , wherein the generating generates the first sound pickup signal having directivity, and the second sound pickup signal having non-directivity, from the first and second signals output by the first microphone and the second microphone.

19. A sound pickup device comprising:

at least one memory device that stores instructions; and

at least one processor that executes the instructions to:

obtains a first sound pickup signal to be generated from a first sound signal output by a first microphone and a second sound pickup signal to be generated from a second sound signal output by a second microphone;

converts the first sound pickup signal and the second sound pickup signal into a first frequency signal and a second frequency signal;

calculates a coherence between the first frequency signal and the second frequency signal;

calculates a ratio of a frequency component of which the calculated coherence exceeds a threshold value with respect to all frequency components; and

controls a level of the first sound pickup signal or the second sound pickup signal according to the calculated ratio.