SOUND QUALITY BY INTELLIGENTLY SELECTING BETWEEN SIGNALS FROM A PLURALITY OF MICROPHONES

• US 20090190769A1
• Filed: 01/29/2008
• Published: 07/30/2009
• Est. Priority Date: 01/29/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Wang, Song, Ramakrishnan, Dinesh, Choy, Eddie L.T.
• Granted Patent: US 8,411,880 B2
• Time in Patent Office: Days
• US Class Current: 381/66
• CPC Class Codes: H03G 3/32 the control being dependent upon ambient noise level or sound level
• CPC Class Codes: H04M 1/0214 Foldable telephones, i.e. with body parts pivoting to an open position around an axis parallel to the plane they define in closed position combined with translation movement H04M1/0235
• CPC Class Codes: H04M 1/035 Improving the acoustic characteristics by means of constructional features of the housing, e.g. ribs, walls, resonating chambers or cavities
• CPC Class Codes: H04M 1/6008 in the transmitter circuit
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• 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

Sound signal reception is improved by utilizing a plurality of microphones to capture sound signals which are then weighed to dynamically adjust signal quality. A first sound signal and a second sound signal are obtained from first and second microphones, respectively, where the first and second sound signals originate from one or more sound sources. A first signal characteristic (e.g., signal power, signal signal-to-noise ratio, etc.) is obtained for the first sound signal and a second signal characteristic is obtained for the second sound signal. The first and second sound signals are weighed or scaled based on their respective first and second signal characteristics. The weighed first and second sound signals are then combined to obtain an output sound signal.

Claims

1. A method for improving sound reception on a mobile device, comprising:

obtaining a first sound signal from a first microphone;

obtaining a second sound signal from a second microphone, wherein each of the first and second sound signals includes at least a portion of a first source signal from a first sound source;

obtaining a first signal characteristic for the first sound signal;

obtaining a second signal characteristic for the second sound signal, wherein both the first and second signal characteristics are associated with a same signal characteristic;

weighing the first and second sound signals based on the first and second signal characteristics; and

combining the weighed first and second sound signals to obtain an output sound signal.

2. The method of claim 1 wherein the first sound signal and the second sound signal are obtained within overlapping time windows.

3. The method of claim 1 wherein the first sound signal and the second sound signal are obtained from independent mixtures of the first source signal and one or more other source signals and noise.

4. The method of claim 1 wherein the first and second microphones are positioned on different surfaces of the mobile device.

5. The method of claim 1 further comprising:

performing additional signal processing on the output sound signal; and

transmitting the output signal to an intended listener over a communication network.

6. The method of claim 5 wherein the additional signal processing includes at least one of echo cancellation, noise reduction, automatic gain control, and coding.

7. The method of claim 5 wherein the communication network is a wireless communication network.

8. The method of claim 1 further comprising:

segmenting the first sound signal into a first plurality of consecutive frames;

segmenting the second sound signal into a second plurality of consecutive frames;

obtaining a first plurality of signal characteristics for the first plurality of consecutive frames for the first sound signal; and

obtaining a second plurality of signal characteristics for the second plurality of consecutive frames for the second sound signal;

wherein the weighing and combining of the first and second sound signals is performed on the first plurality of signal characteristics and the second plurality of signal characteristics.

9. The method of claim 1 wherein weighing the first and second sound signals includes

comparing the first signal characteristic and second signal characteristic;

scaling the first sound signal by zero and scaling the second sound signal by one if the second sound signal provides better sound quality than the first sound signal; and

scaling the first sound signal by one and scaling the second sound signal by zero if the first sound signal provides better sound quality than the second sound signal.

10. The method of claim 9 wherein

scaling the first sound signal by zero and scaling the second sound signal by one is performed if the second signal characteristic is greater than the first signal characteristic by at least a minimum threshold amount if the first sound signal is currently being used;

and

scaling the first sound signal by one and scaling the second sound signal by zero is performed if the first signal characteristic is greater than the second signal characteristic by at least the minimum threshold amount if the second sound signal is currently being used.

11. The method of claim 1 further comprising:

determining a first signal-to-noise ratio for the first sound signal;

determining a second signal-to-noise ratio for the second sound signal;

weighing the first sound signal to provide a greater contribution to the output sound signal than the second sound signal if the first signal-to-noise ratio is greater than the second signal-to-noise ratio; and

weighing the second sound signal to provide a greater contribution to the output sound signal than the first sound signal if the second signal-to-noise ratio is greater than the first signal-to-noise ratio.

12. The method of claim 11 further comprising:

segmenting the first sound signal into a first plurality of consecutive frames;

obtaining a first plurality of consecutive signal powers for the first plurality of consecutive frames for the first sound signal; and

searching for a minimum signal power in the plurality of consecutive signal powers for the first plurality of consecutive frames to obtain a noise floor estimate with which to obtain the first signal-to-noise ratio.

13. The method of claim 1 further comprising:

calibrating the first and second microphones to have substantially the same sensitivity; and

weighing the first sound signal to provide a greater contribution to the output sound signal than the second sound signal if the first signal characteristic is greater than the second signal characteristic; and

weighing the second sound signal to provide a greater contribution to the output sound signal than the first sound signal if the second signal characteristic is greater than the first signal characteristic.

14. The method of claim 13 wherein the first and second signal characteristics are signal powers.

15. The method of claim 1, wherein if the second sound signal provides improved sound quality over the first sound signal, further comprising:

transitioning from the first sound signal to the second sound signal by blending the first sound signal with the second sound signal; and

gradually decreasing the contribution of the first sound signal and increasing the contribution of the second sound signal.

16. The method of claim 15 wherein the contribution from the first sound signal is decreased and the contribution from the second sound signal is increased according to linear functions.

17. The method of claim 15 wherein the contribution from the first sound signal is decreased and the contribution from the second sound signal is increased according to non-linear functions.

18. The method of claim 1 further comprising:

selecting the first and second microphones from a plurality of three or more microphones on the mobile device, wherein such selection is performed based on which of the three or more microphones has the best signal quality.

19. The method of claim 1 further comprising:

obtaining at least one additional sound signal from at least one additional microphone, wherein the at least one additional sound signal includes at least a portion of a first source signal from a first sound source;

obtaining at least one additional signal characteristic for the at least one additional sound signal;

weighing the at least one additional sound signal and the first and second sound signals based on the first signal characteristic, second signal characteristic, and the at least one additional signal characteristic; and

combining the weighed first sound signal, second sound signal, and at least one additional sound signal to obtain an output sound signal.

20. A mobile device comprising:

a first microphone configured to obtain a first sound signal;

a second microphone configured to obtain a second sound signal, wherein each of the first and second sound signals includes at least a portion of a first source signal from a first sound source; and

a signal selection module configured to

obtain a first signal characteristic for the first sound signal;

obtain a second signal characteristic for the second sound signal, wherein both the first and second signal characteristics are associated with a same signal characteristic;

weigh the first and second sound signals based on the first and second signal characteristics; and

combine the weighed first and second sound signals to obtain an output sound signal.

21. The mobile device of claim 20 further comprising:

a signal processor configured to perform at least one of echo cancellation, noise reduction, automatic gain control, and coding on the output signal; and

a transmitter configured to transmit the processed output signal via a wireless communication network.

22. The mobile device of claim 20 wherein the first sound signal and the second sound signal are obtained from an acoustic signal within overlapping time windows, and the first and second microphones are positioned on different surfaces of the mobile device.

23. The mobile device of claim 20 further comprising:

a first analog-to-signal converter configured to segment the first sound signal into a first plurality of consecutive frames;

a second analog-to-signal converter configured to segment the second sound signal into a second plurality of consecutive frames;

wherein the signal selection module is further configured to

obtain a plurality of consecutive signal characteristics for the first plurality of consecutive frames for the first sound signal; and

obtain a second plurality of consecutive signal characteristics for the second plurality of consecutive frames for the second sound signal;

wherein the weighing and combining of the first and second sound signals is performed based on the first plurality of signal characteristics and the second plurality of signal characteristics.

24. The mobile device of claim 20 wherein the signal selection module is further configured to

compare the first signal characteristic and second signal characteristic;

scale the first sound signal by zero and scaling the second sound signal by one if the second sound signal provides better sound quality than the first sound signal; and

scale the first sound signal by one and scaling the second sound signal by zero if the first sound signal provides better sound quality than the second sound signal.

25. The mobile device of claim 24 wherein the signal selection module is further configured to

scale the first sound signal by zero and scaling the second sound signal by one is performed if the second signal characteristic is greater than the first signal characteristic by at least a minimum threshold amount if the first sound signal is currently being used;

and

scale the first sound signal by one and scaling the second sound signal by zero is performed if the first signal characteristic is greater than the second signal characteristic by at least the minimum threshold amount if the second sound signal is currently being used.

26. The mobile device of claim 20 wherein the signal selection module is further configured to

determine a first signal-to-noise ratio for the first sound signal;

determine a second signal-to-noise ratio for the second sound signal;

weigh the first sound signal to provide a greater contribution to the output sound signal than the second sound signal if the first signal-to-noise ratio is greater than the second signal-to-noise ratio; and

weigh the second sound signal to provide a greater contribution to the output sound signal than the first sound signal if the second signal-to-noise ratio is greater than the first signal-to-noise ratio.

27. The mobile device of claim 20 wherein the signal selection module is further configured to

select the first and second microphones from a plurality of three or more microphones on the mobile device, wherein such selection is performed based on which of the three or more microphones has the best signal quality.

28. The mobile device of claim 20 wherein the signal selection module is further configured to

obtain at least one additional sound signal from at least one additional microphone, wherein the at least one additional sound signal includes at least a portion of the first source signal from the first sound source;

obtain at least one additional signal characteristic for the at least one additional sound signal;

weight the at least one additional sound signal and the first and second sound signals based on the first signal characteristic, second signal characteristic, and the at least one additional signal characteristic; and

combine the weighed first sound signal, second sound signal, and at least one additional sound signal to obtain an output sound signal.

29. A mobile device comprising:

means for obtaining a first sound signal from a first microphone;

means for obtaining a second sound signal from a second microphone, wherein each of the first and second sound signals include at least a portion of a first source signal from a first sound source;

means for obtaining a first signal characteristic for the first sound signal;

means for obtaining a second signal characteristic for the second sound signal, wherein both the first and second signal characteristics are associated with a same signal characteristic;

means for weighing the first and second sound signals based on the first and second signal characteristics; and

means for combining the weighed first and second sound signals to obtain an output sound signal.

30. The mobile device of claim 29 further comprising:

means for performing at least one of echo cancellation, noise reduction, automatic gain control, and coding on the output signal; and

means for transmitting the processed output signal via a wireless communication network.

31. The mobile device of claim 29 further comprising:

means for comparing the first signal characteristic and second signal characteristic;

means for scaling the first sound signal by zero and scaling the second sound signal by one if the second sound signal provides better sound quality than the first sound signal; and

means for scaling the first sound signal by one and scaling the second sound signal by zero if the first sound signal provides better sound quality than the second sound signal.

32. The mobile device of claim 29 further comprising:

means for weighing the first sound signal to provide a greater contribution to the output sound signal than the second sound signal if the first signal characteristic is greater than the second signal characteristic; and

means for weighing the second sound signal to provide a greater contribution to the output sound signal than the first sound signal if the second signal characteristic is greater than the first signal characteristic.

33. A circuit for improving sound quality, wherein the circuit is adapted to:

obtain a first sound signal from a first microphone;

obtain a second sound signal from a second microphone, wherein each of the first and second sound signals include at least a portion of a first source signal from a first sound source;

obtain a first signal characteristic for the first sound signal;

obtain a second signal characteristic for the second sound signal, wherein both the first and second signal characteristics are associated with a same signal characteristic;

weight the first and second sound signals based on the first and second signal characteristics; and

combine the weighed first and second sound signals to obtain an output sound signal.

34. The circuit of claim 33, wherein the circuit is further adapted to

scale the first sound signal by zero and scaling the second sound signal by one if the second sound signal provides better sound quality than the first sound signal;

and

scale the first sound signal by one and scaling the second sound signal by zero if the first sound signal provides better sound quality than the second sound signal.

35. The circuit of claim 33, wherein the circuit is further adapted to

weight the first sound signal to provide a greater contribution to the output sound signal than the second sound signal if the first signal characteristic is greater than the second signal characteristic;

and

weight the second sound signal to provide a greater contribution to the output sound signal than the first sound signal if the second signal characteristic is greater than the first signal characteristic.

36. The circuit of claim 33, wherein the circuit is an integrated circuit.

37. A computer-readable medium comprising instructions for improving sound signal reception, which when executed by a processor causes the processor to

obtain a first sound signal from a first microphone;

obtain a second sound signal from a second microphone, wherein each of the first and second sound signals include at least a portion of a first source signal from a first sound source;

obtain a first signal characteristic for the first sound signal;

obtain a second signal characteristic for the second sound signal, wherein both the first and second signal characteristics are associated with a same signal characteristic;

weight the first and second sound signals based on the first and second signal characteristics; and

combine the weighed first and second sound signals to obtain an output sound signal.

38. The computer-readable medium of claim 37 further comprising instructions for which when executed by a processor causes the processor to

select the first and second microphones from a plurality of three or more microphones, wherein such selection is performed based on which of the three or more microphones has the best signal quality.