Sound field spatial stabilizer with echo spectral coherence compensation
In a system and method for maintaining the spatial stability of a sound field a balance gain may be calculated for two or more microphone signals. The balance gain may be associated with a spatial image in the sound field. Signal values may be calculated for each of the microphone. The signal values may be signal estimates or signal gains calculated to improve a characteristic of the microphone signals. The differences between the signal values associated with each microphone signal may be limited although some difference between signal values may be allowable. One or more microphone signals are adjusted responsive to the two or more balance gains and the signal gains to maintain the spatial stability of the sound field. The adjustments of one or more microphone signals may include mixing of two or more microphone. The signal gains are applied to the two or more microphone signals.
1. A computer implemented method for maintaining spatial stability of a sound field comprising:
calculating balance gains for each of two or more microphone signals;
calculating one or more signal values for each of the two or more microphone signals;
calculating a predicted echo for a received audio signal;
calculating a pair-wise echo spectral coherence between the predicted echo and each of the two or more microphone signals ;
calculating a pair-wise spectral coherence between each of the two or more microphone signals; and
gain adjusting the two or more microphone signals responsive to the calculated balance gains, the one or more signal values, the echo spectral coherence and the pair-wise spectral coherence for each of the two or more microphone signals.
2. The computer implemented method of claim 1 , where the one or more signal values comprise one or more of an estimated background noise and a calculated suppression gain.
3. The computer implemented method of claim 2 where calculating the suppression gain comprises one or more of a noise reduction calculation and an echo cancellation calculation.
4. The computer implemented method of claim 3 , where the noise reduction calculation comprises any one or more of a wind noise reduction calculation, transients noise reduction calculation, a road noise reduction calculation, a repetitive noise reduction calculation and an engine noise reduction calculation.
5. The computer implemented method of claim 1 , where the received audio signal is a far side audio signal.
6. The computer implemented method of claim 1 , where gain adjusting the two or more microphone signals responsive to an increased pair-wise spectral coherence includes reducing the balance gains for a higher amplitude microphone signal of the two or more microphone signals.
7. The computer implemented method of claim 6 , where the increased pair-wise spectral coherence is greater than about 0.85.
8. The computer implemented method of claim 7 , where a pair-wise spectral coherence range between about 0.85 and about 1.0 is resealed to between 0 and about 1.
9. The computer implemented method of claim 1 , where gain adjusting the two or more microphone signals responsive to an increased pair-wise echo spectral coherence includes increasing the balance gains for the two or more microphone signals.
10. The computer implemented method of claim 9 , where the increased pair-wise echo spectral coherence is greater than about 0.85.
11. The computer implemented method of claim 10 , where a pair-wise echo spectral coherence range between about 0.85 and about 1.0 is resealed to between 0 and about 1.
12. The computer implemented method of claim 1 , where gain adjusting the two or more microphone signals responsive to an increased produce of the pair-wise spectral coherence and one minus the pair-wise spectral coherence includes increasing the balance gains for a higher amplitude microphone signal of the two or more microphone signals.
13. The computer implemented method of claim 1 , further comprising generating a set of sub-bands for each of the two or more microphone signals using a subband filter or a Fast Fourier Transform.
14. The computer implemented method of claim 1 , further comprising generating a set of sub-bands for each of the two or more microphone signals according to a critical, octave, mel, or bark band spacing technique.
15. A system for maintaining spatial stability of a sound field comprising:
a balance calculator to calculate balance gains for each of two or more microphone signals;
two or more signal value generators, each one associated with one of the two or more microphone signals, to calculate one or more signal values;
an echo filter to calculate a predicted echo for a received audio signal;
a coherence echo calculator to calculate a pair-wise echo spectral coherence between the predicted echo and each of the two or more microphone signals;
a coherence calculator to calculate a pair-wise spectral coherence between each of the two or more microphone signals; and
a gain adjuster to adjust the two or more microphone signals responsive to the calculated balance gains, the one or more signal values, the echo spectral coherence and the pair-wise spectral coherence for each of the two or more microphone signals.
16. The system for maintaining spatial stability of a sound field of claim 15 , where the one or more signal values comprise one or more of an estimated background noise and a calculated suppression gain.
17. The system for maintaining spatial stability of a sound field of claim 16 where calculating the suppression gain comprises one or more of a noise reduction calculation and an echo cancellation calculation.
18. The system for maintaining spatial stability of a sound field of claim 17 , where the noise reduction calculation comprises any one or more of a wind noise reduction calculation, transients noise reduction calculation, a road noise reduction calculation, a repetitive noise reduction calculation and an engine noise reduction calculation.
19. The system for maintaining spatial stability of a sound field of claim 15 , where the received audio signal is a far side audio signal.
20. The system for maintaining spatial stability of a sound field of claim 15 , where gain adjusting the two or more microphone signals responsive to an increased pair-wise spectral coherence includes reducing the balance gains for a higher amplitude microphone signal of the two or more microphone signals.
21. The system for maintaining spatial stability of a sound field of claim 20 , where the increased pair-wise spectral coherence is greater than about 0.85.
22. The system for maintaining spatial stability of a sound field of claim 21 , where a pair-wise spectral coherence range between about 0.85 and about 1.0 is rescaled to between 0 and about 1.
23. The system for maintaining spatial stability of a sound field of claim 15 , where gain adjusting the two or more microphone signals responsive to an increased pair-wise echo spectral coherence includes increasing the balance gains for the two or more microphone signals.
24. The system for maintaining spatial stability of a sound field of claim 23 , where the increased pair-wise echo spectral coherence is greater than about 0.85.
25. The system for maintaining spatial stability of a sound field of claim 24 , where a pair-wise echo spectral coherence range between 0.85 and 1.0 is rescaled to between 0 and 1.
26. The system for maintaining spatial stability of a sound field of claim 15 , where gain adjusting the two or more microphone signals responsive to an increased produce of the pair-wise spectral coherence and one minus the pair-wise spectral coherence includes increasing the balance gains for a higher amplitude microphone signal of the two or more microphone signals.
27. The system for maintaining spatial stability of a sound field of claim 15 , further comprising generating a set of sub-bands for each of the two or more microphone signals using a subband filter or a Fast Fourier Transform.
28. The system for maintaining spatial stability of a sound field of claim 15 , further comprising generating a set of sub-bands for each of the two or more microphone signals according to a critical, octave, mel, or bark band spacing technique.