Systems, methods, apparatus, and computer-readable media for phase-based processing of multichannel signal

• US 8,620,672 B2
• Filed: 06/08/2010
• Issued: 12/31/2013
• Est. Priority Date: 06/09/2009
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Visser, Erik, Liu, Ernan
• Primary Examiner(s): Han, Qi
• Application Number:
  US12/796,566
• Publication Number:
  US 20100323652A1
• Time in Patent Office: 1,302 Days
• Field of Search: 704/500, 704/501, 704/503, 704/200, 704/205, 704/226
• US Class Current: 704/500
• CPC Class Codes: G10L 2021/02166 Microphone arrays; Beamforming
• CPC Class Codes: H04R 2205/022 Plurality of transducers corresponding to a plurality of sound channels in each earpiece of headphones or in a single enclosure
• CPC Class Codes: H04R 29/006 Microphone matching
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

Phase-based processing of a multichannel signal, and applications including proximity detection, are disclosed.

Claims

1. A method of processing a multichannel signal, said method comprising:

for each of a plurality of different frequency components of the multichannel signal, calculating a difference between a phase of the frequency component in a first channel of the multichannel signal and a phase of the frequency component in a second channel of the multichannel signal, to obtain a plurality of calculated phase differences;

calculating a level of the first channel and a corresponding level of the second channel;

based on the calculated level of the first channel, the calculated level of the second channel, and at least one of the plurality of calculated phase differences, calculating an updated value of a gain factor; and

producing a processed multichannel signal by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel,

wherein each channel of the multichannel signal is based on a signal produced by a corresponding microphone, among an array of microphones, in response to an acoustic environment of the microphone.

2. The method of processing a multichannel signal according to claim 1, wherein said calculated level of the first channel is a calculated energy of the first channel in a first frequency subband, and wherein said calculated level of the second channel is a calculated energy of the second channel in the first frequency subband, and

wherein said amplitude of the first channel is an amplitude of the first channel in the first frequency subband, and wherein said corresponding amplitude of the second channel is an amplitude of the second channel in the first frequency subband, and

wherein said method comprises:

calculating an energy of the first channel in a second frequency subband that is different than the first frequency subband;

calculating an energy of the second channel in the second frequency subband; and

based on the calculated energy of the first channel in the second frequency subband, the calculated energy of the second channel in the second frequency subband, and at least one of the plurality of calculated phase differences, calculating an updated value of a second gain factor,

wherein said producing a processed multichannel signal includes producing the processed multichannel signal by altering, according to the updated value of the second gain factor, an amplitude of the second channel in the second frequency subband relative to an amplitude of the first channel in the second frequency subband.

3. The method of processing a multichannel signal according to claim 1, wherein said method comprises calculating a value of a coherency measure that indicates a degree of coherence among the directions of arrival of at least the plurality of different frequency components, based on information from the plurality of calculated phase differences;

and

wherein said calculating an updated value of a gain factor is based on the calculated value of the coherency measure.

4. The method of processing a multichannel signal according to claim 3, wherein said altering an amplitude of the first channel relative to a corresponding amplitude of the second channel is performed in response to a result of comparing said value of the coherency measure to a threshold value.

5. The method of processing a multichannel signal according to claim 3, wherein said method comprises, based on a relation between a level of a first channel of the processed multichannel signal and a level of a second channel of the processed multichannel signal, and in response to a result of comparing said value of the coherency measure to a threshold value, updating a noise estimate according to acoustic information from at least one of the first and second channels of the multichannel signal.

6. The method of processing a multichannel signal according to claim 1, wherein said method includes selecting the plurality of different frequency components based on an estimated pitch frequency of the multichannel signal.

7. The method of processing a multichannel signal according to claim 1, wherein said updated value of a gain factor is based on a ratio between the calculated level of the first channel and the calculated level of the second channel.

8. The method of processing a multichannel signal according to claim 1, wherein said producing a processed multichannel signal by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel comprises reducing an imbalance between the calculated levels of the first and second channels.

9. The method of processing a multichannel signal according to claim 1, wherein said producing a processed multichannel signal includes altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel in each of a plurality of consecutive segments of the multichannel signal.

10. The method of processing a multichannel signal according to claim 1, wherein said method comprises, based on a relation between a level of a first channel of the processed multichannel signal and a level of a second channel of the processed multichannel signal, indicating the presence of voice activity.

11. The method of processing a multichannel signal according to claim 10, wherein said method comprises, based on information from said plurality of calculated phase differences, indicating that the multichannel signal is directionally coherent in an endfire direction of the array of microphones, and

wherein said indicating the presence of voice activity is performed in response to said indicating that the multichannel signal is directionally coherent.

12. The method of processing a multichannel signal according to claim 1, wherein said plurality of different frequency components of the multichannel signal is within a range of acoustic frequencies.

13. The method of processing a multichannel signal according to claim 1, wherein at least one among said calculating a difference, calculating a level, calculating an updated value, and producing the processed multichannel signal is performed by a device configured to process signals having acoustic frequencies.

14. The method of processing a multichannel signal according to claim 1, wherein said processed multichannel signal represents an acoustic environment of the array of microphones.

15. The method of processing a multichannel signal according to claim 1, wherein said method comprises, based on information from the plurality of calculated phase differences, determining whether a segment of the multichannel signal is acoustically balanced.

16. The method of processing a multichannel signal according to claim 15, wherein said calculating an updated value of a gain factor is performed in response to said determining.

17. The method of processing a multichannel signal according to claim 15, wherein said method comprises, for each among a plurality of gain factors, and in response to said determining, calculating an updated value of the gain factor that is based on a corresponding one of the calculated phase differences.

18. The method of processing a multichannel signal according to claim 1, wherein said method comprises, based on information from the plurality of calculated phase differences, determining whether a subband of the multichannel signal is acoustically balanced.

19. A non-transitory computer-readable storage medium comprising tangible features that when read by a processor cause the processor to:

calculate, for each of a plurality of different frequency components of the multichannel signal, a difference between a phase of the frequency component in a first channel of the multichannel signal and a phase of the frequency component in a second channel of the multichannel signal, to obtain a plurality of calculated phase differences;

calculate a level of the first channel and a corresponding level of the second channel;

calculate an updated value of a gain factor, based on the calculated level of the first channel, the calculated level of the second channel, and at least one of the plurality of calculated phase differences; and

produce a processed multichannel signal by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel,

wherein each channel of the multichannel signal is based on a signal produced by a corresponding microphone, among an array of microphones, in response to an acoustic environment of the microphone.

20. An apparatus for processing a multichannel signal, said apparatus comprising:

a first calculator configured to obtain a plurality of calculated phase differences by calculating, for each of a plurality of different frequency components of the multichannel signal, a difference between a phase of the frequency component in a first channel of the multichannel signal and a phase of the frequency component in a second channel of the multichannel signal;

a second calculator configured to calculate a level of the first channel and a corresponding level of the second channel;

a third calculator configured to calculate an updated value of a gain factor, based on the calculated level of the first channel, the calculated level of the second channel, and at least one of the plurality of calculated phase differences; and

a gain control element configured to produce a processed multichannel signal by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel,

wherein at least one among said first calculator, said second calculator, said third calculator, and said gain control element is implemented by at least one processor, and

wherein each channel of the multichannel signal is based on a signal produced by a corresponding microphone, among an array of microphones, in response to an acoustic environment of the microphone.

21. The apparatus according to claim 20, wherein said calculated level of the first channel is a calculated energy of the first channel in a first frequency subband, and wherein said calculated level of the second channel is a calculated energy of the second channel in the first frequency subband, and

wherein said amplitude of the first channel is an amplitude of the first channel in the first frequency subband, and wherein said corresponding amplitude of the second channel is an amplitude of the second channel in the first frequency subband, and

wherein said second calculator is configured to calculate an energy of the first channel in a second frequency subband that is different than the first frequency subband, and to calculate an energy of the second channel in the second frequency subband, and

wherein said third calculator is configured to calculating an updated value of a second gain factor, based on the calculated energy of the first channel in the second frequency subband, the calculated energy of the second channel in the second frequency subband, and at least one of the plurality of calculated phase differences,

wherein said gain control element is configured to produce the processed multichannel signal by altering, according to the updated value of the second gain factor, an amplitude of the second channel in the second frequency subband relative to an amplitude of the first channel in the second frequency subband.

22. The apparatus according to claim 20, wherein said third calculator is configured to calculate a value of a coherency measure that indicates a degree of coherence among the directions of arrival of at least the plurality of different frequency components, based on information from the plurality of calculated phase differences;

and

wherein said third calculator is configured to calculate the updated value of a gain factor based on the calculated value of the coherency measure.

23. The apparatus according to claim 22, wherein said third calculator is configured to compare said value of the coherency measure to a threshold value, and

wherein said gain control element is configured to alter an amplitude of the first channel relative to a corresponding amplitude of the second channel in response to a result of said comparing said value of the coherency measure to a threshold value.

24. The apparatus according to claim 22, wherein said method comprises, based on a relation between a level of a first channel of the processed multichannel signal and a level of a second channel of the processed multichannel signal, and in response to a result of comparing said value of the coherency measure to a threshold value, updating a noise estimate according to acoustic information from at least one of the first and second channels of the multichannel signal.

25. The apparatus according to claim 20, wherein said phase difference calculator is configured to select the plurality of different frequency components based on an estimated pitch frequency of the multichannel signal.

26. The apparatus according to claim 20, wherein said updated value of a gain factor is based on a ratio between the calculated level of the first channel and the calculated level of the second channel.

27. The apparatus according to claim 20, wherein said gain control element is configured to reduce an imbalance between the calculated levels of the first and second channels by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel.

28. The apparatus according to claim 20, wherein said gain control element is configured to produce the processed multichannel signal by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel in each of a plurality of consecutive segments of the multichannel signal.

29. The apparatus according to claim 20, wherein said apparatus includes a voice activity detector configured to indicate the presence of voice activity based on a relation between a level of a first channel of the processed multichannel signal and a level of a second channel of the processed multichannel signal.

30. An apparatus for processing a multichannel signal, said apparatus comprising:

means for calculating, for each of a plurality of different frequency components of the multichannel signal, a difference between a phase of the frequency component in a first channel of the multichannel signal and a phase of the frequency component in a second channel of the multichannel signal, to obtain a plurality of calculated phase differences;

means for calculating a level of the first channel and a corresponding level of the second channel;

means for calculating an updated value of a gain factor, based on the calculated level of the first channel, the calculated level of the second channel, and at least one of the plurality of calculated phase differences; and

means for producing a processed multichannel signal by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel,

wherein at least one among said means for calculating a difference, said means for calculating a level, said means for calculating an updated value, and said means for producing is implemented by at least one processor, and

wherein each channel of the multichannel signal is based on a signal produced by a corresponding microphone, among an array of microphones, in response to an acoustic environment of the microphone.

31. The apparatus according to claim 30, wherein said calculated level of the first channel is a calculated energy of the first channel in a first frequency subband, and wherein said calculated level of the second channel is a calculated energy of the second channel in the first frequency subband, and

wherein said amplitude of the first channel is an amplitude of the first channel in the first frequency subband, and wherein said corresponding amplitude of the second channel is an amplitude of the second channel in the first frequency subband, and

wherein said apparatus comprises:

means for calculating an energy of the first channel in a second frequency subband that is different than the first frequency subband;

means for calculating an energy of the second channel in the second frequency subband; and

means for calculating an updated value of a second gain factor, based on the calculated energy of the first channel in the second frequency subband, the calculated energy of the second channel in the second frequency subband, and at least one of the plurality of calculated phase differences,

wherein said means for producing a processed multichannel signal includes means for producing the processed multichannel signal by altering, according to the updated value of the second gain factor, an amplitude of the second channel in the second frequency subband relative to an amplitude of the first channel in the second frequency subband.

32. The apparatus according to claim 30, wherein said apparatus comprises means for calculating a value of a coherency measure that indicates a degree of coherence among the directions of arrival of at least the plurality of different frequency components, based on information from the plurality of calculated phase differences;

and

wherein said means for calculating an updated value of a gain factor is configured to calculate the updated value of the gain factor based on the calculated value of the coherency measure.

33. The apparatus according to claim 32, wherein said means for altering an amplitude of the first channel relative to a corresponding amplitude of the second channel is configured to perform such altering in response to an output of said means for comparing said value of the coherency measure to a threshold value.

34. The apparatus according to claim 32, wherein said apparatus comprises means for updating a noise estimate according to acoustic information from at least one of the first and second channels of the multichannel signal, based on a relation between a level of a first channel of the processed multichannel signal and a level of a second channel of the processed multichannel signal, and in response to a result of comparing said value of the coherency measure to a threshold value.

35. The apparatus according to claim 30, wherein said apparatus includes means for selecting the plurality of different frequency components based on an estimated pitch frequency of the multichannel signal.

36. The apparatus according to claim 30, wherein said updated value of a gain factor is based on a ratio between the calculated level of the first channel and the calculated level of the second channel.

37. The apparatus according to claim 30, wherein said means for producing a processed multichannel signal by altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel is configured to reduce an imbalance between the calculated levels of the first and second channels.

38. The apparatus according to claim 30, wherein said means for producing a processed multichannel signal includes means for altering, according to the updated value, an amplitude of the second channel relative to a corresponding amplitude of the first channel in each of a plurality of consecutive segments of the multichannel signal.

39. The apparatus according to claim 30, wherein said apparatus comprises means for indicating the presence of voice activity, based on a relation between a level of a first channel of the processed multichannel signal and a level of a second channel of the processed multichannel signal.