SIGNALING MICROPHONE COVERING TO THE USER

• US 20090196429A1
• Filed: 01/31/2008
• Published: 08/06/2009
• Est. Priority Date: 01/31/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Satyanarayanan, Ravi, Wang, Song, Ramakrishnan, Dinesh, Choy, Eddie L.T.
• Granted Patent: US 8,374,362 B2
• Time in Patent Office: Days
• US Class Current: 381/26
• 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 29/004 for microphones H04R29/007 takes precedence
• 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

A mechanism is provided that monitors secondary microphone signals, in a multi-microphone mobile device, to warn the user if one or more secondary microphones are covered while the mobile device is in use. In one example, smoothly averaged power estimates of the secondary microphones may be computed and compared against the noise floor estimate of a primary microphone. Microphone covering detection may be made by comparing the secondary microphone smooth power estimates to the noise floor estimate for the primary microphone. In another example, the noise floor estimates for the primary and secondary microphone signals may be compared to the difference in the sensitivity of the first and second microphones to determine if the secondary microphone is covered. Once detection is made, a warning signal may be generated and issued to the user.

Claims

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

receiving a first acoustic signal via a primary microphone to obtain a primary sound signal;

receiving a second acoustic signal via a secondary microphone to obtain a secondary sound signal;

determining a first signal characteristic for the primary sound signal;

determining a second signal characteristic for the secondary sound signal;

determining whether the secondary microphone is obstructed based on the first signal characteristic and second signal characteristic; and

providing a warning indicating that the secondary microphone is obstructed.

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

3. The method of claim 1 wherein the secondary sound signal is used to improve the sound quality of the primary sound signal.

4. The method of claim 1 wherein determining whether the secondary microphone is obstructed based on the first signal characteristic and second signal characteristic includes,

determining whether a ratio between the second signal characteristic and first signal characteristic is less than a threshold;

and

providing the warning if the ratio is less than the threshold.

5. The method of claim 4 further comprising:

obtaining a first sensitivity corresponding to a primary microphone and a second sensitivity corresponding to a secondary microphone.

6. The method of claim 5 further comprising:

obtaining the threshold based on the difference between the first sensitivity and the second sensitivity.

7. The method of claim 5 wherein the first sensitivity of the primary microphone and second sensitivity of the secondary microphone are obtained for a given level of sound pressure.

8. The method of claim 1, further comprising:

processing the primary sound signal to either reduce noise or enhance sound quality by using the secondary sound signal; and

transmitting the processed primary sound signal to an intended listener over a communication network.

9. The method of claim 1 wherein the first signal characteristic is a first noise level for the primary sound signal and the second signal characteristic is a second noise level for the secondary sound signal.

10. The method of claim 9, wherein the first noise level is a first noise floor level and the second noise level is a second noise floor level, and further comprising:

smoothening the first and second noise floor levels for the first and second sound signals.

11. The method of claim 9, wherein obtaining the first signal characteristic for the primary sound signal includes

segmenting the primary sound signal it into a first plurality of frames;

estimating a block power for each of the first plurality of frames; and

searching for a minimum energy term in the first plurality of frames to obtain a first noise floor estimate for the primary sound signal, wherein the first noise floor estimate is the noise level for the primary sound signal.

12. The method of claim 11, wherein obtaining the second signal characteristic for the secondary sound signal includes

segmenting the secondary sound signal it into a second plurality of frames;

estimating a block power for each of the second plurality of frames; and

searching for a minimum energy term in the second plurality of frames to obtain a second noise floor estimate for the primary sound signal, wherein the second noise floor estimate is the noise level for the secondary sound signal.

13. The method of claim 11, wherein determining whether the secondary microphone is obstructed includes

obtaining a ratio of the second noise floor estimate to the first noise floor estimate;

and

determining whether the ratio is less than a threshold.

14. The method of claim 1 wherein the warning is provided through at least one of an sound signal, a vibration of the mobile device, and a visual indicator.

15. The method of claim 1 wherein the first signal characteristic is a first noise level for the primary sound signal and the second signal characteristic is a second power level for the secondary sound signal.

16. The method of claim 1 further comprising:

obtaining a block power estimate for the secondary sound signal for the secondary microphone;

obtaining a smoothening factor for the secondary sound signal;

obtaining a smooth block power estimate for the secondary sound signal based on the smoothening factor and the block power estimate;

obtaining a first noise floor estimate for a primary microphone signal block for the primary microphone;

obtaining a ratio between the smooth block power estimate and the first noise floor estimate; and

determining whether the ratio is less than a threshold.

17. The method of claim 1 further comprising:

dynamically selecting the primary microphone from a plurality of microphones based on which microphone has either the highest signal energy or highest signal-to-noise ratio at a particular period of time.

18. A mobile device comprising:

a primary microphone configured to obtain a first sound signal;

a secondary microphone configured to obtain a second sound signal;

a secondary microphone cover detection module is configured to

determine a first signal characteristic for the primary sound signal;

determine a second signal characteristic for the secondary sound signal;

determine whether the secondary microphone is obstructed based on the first signal characteristic and second signal characteristic; and

provide a warning indicating that the secondary microphone is obstructed.

19. The mobile device of claim 18 wherein the warning is provided through at least one of an audio signal, a vibration of the mobile device, and a visual indicator.

20. The mobile device of claim 18 wherein the primary sound signal and the secondary sound signal are obtained within overlapping time windows.

21. The mobile device of claim 18 wherein the secondary sound signal is used to improve the sound quality of the primary sound signal.

22. The mobile device of claim 18 wherein determining whether the secondary microphone is obstructed based on the first signal characteristic and second signal characteristic, the secondary microphone cover detection module is further configured to

determine whether a ratio between the second signal characteristic and first signal characteristic is less than a threshold.

23. The mobile device of claim 22, wherein the secondary microphone cover detection module is further configured to

obtain a first sensitivity corresponding to the primary microphone and a second sensitivity corresponding to the secondary microphone, wherein the first sensitivity of the primary microphone and second sensitivity of the secondary microphone are obtained for a given level of sound pressure;

and

obtain a threshold based on the difference between the first sensitivity and the second sensitivity.

24. The mobile device of claim 18, wherein the secondary microphone cover detection module is further configured to

process the primary sound signal to either reduce noise or enhance sound quality by using the secondary sound signal;

and

transmit the processed primary sound signal to an intended listener over a communication network.

25. The mobile device of claim 18, wherein the primary and secondary microphones are selected from a plurality of microphones mounted on different surfaces of the mobile device.

26. The mobile device of claim 25, wherein the secondary microphone cover detection module is further configured to

dynamically select the primary microphone from the plurality of microphones based on which microphone has either the highest signal energy or highest signal-to-noise ratio at a particular period of time.

27. The mobile device of claim 18 wherein the first signal characteristic is a first noise floor estimate for the primary sound signal and the second signal characteristic is a second noise floor estimate for the secondary sound signal, and the secondary microphone cover detection module is further configured to

determine whether a ratio between the second noise floor estimate and the first noise floor estimate is less than a threshold.

28. The mobile device of claim 18, wherein the first signal characteristic is a first noise floor estimate for the primary sound signal and the second signal characteristic is a second smoothened power estimate for the secondary sound signal, and the secondary microphone cover detection module is further configured to

determine whether a ratio between the second smoothened power estimate and the first noise floor estimate is less than a threshold.

29. A mobile device comprising:

means for receiving a first acoustic signal via a primary microphone to obtain a primary sound signal;

means for receiving a second acoustic signal via a secondary microphone to obtain a secondary sound signal;

means for determining a first signal characteristic for the primary sound signal;

means for determining a second signal characteristic for the secondary sound signal;

means for determining whether the secondary microphone is obstructed based on the first signal characteristic and second signal characteristic; and

means for providing a warning indicating that the secondary microphone is obstructed.

30. The mobile device of claim 29 wherein the first signal characteristic is a first noise floor estimate for the primary sound signal and the second signal characteristic is a second noise floor estimate for the secondary sound signal.

31. The mobile device of claim 29, wherein the first signal characteristic is a first noise floor estimate for the primary sound signal and the second signal characteristic is a second smoothened power estimate for the secondary sound signal.

32. A circuit for improving sound capture, wherein the circuit is adapted to receive a first acoustic signal via a primary microphone to obtain a primary sound signal;

receive a second acoustic signal via a secondary microphone to obtain a secondary sound signal;

obtain a first signal characteristic for the primary sound signal;

obtain a second signal characteristic for the secondary sound signal;

determine whether the secondary microphone is obstructed based on the first signal characteristic and second signal characteristic; and

provide a warning indicating that the secondary microphone is obstructed.

33. The circuit of claim 32 wherein the first signal characteristic is a first noise floor estimate for the primary sound signal and the second signal characteristic is a second noise floor estimate for the secondary sound signal, and, to determine whether the secondary microphone is obstructed, the circuit is further adapted to

determine whether a ratio between the second noise floor estimate and the first noise floor estimate is less than a threshold.

34. The circuit of claim 32, wherein the first signal characteristic is a first noise floor estimate for the primary sound signal and the second signal characteristic is a second smoothened power estimate for the secondary sound signal, and, to determine whether the secondary microphone is obstructed, the circuit is further adapted to

determine whether a ratio between the second smoothened power estimate and the first noise floor estimate is less than a threshold.

35. The circuit of claim 32, wherein the circuit is an integrated circuit.

36. A computer-readable medium comprising instructions improving sound capture on a mobile device, which when executed by a processor causes the processor to

receive a first acoustic signal via a primary microphone to obtain a primary sound signal;

receive a second acoustic signal via a secondary microphone to obtain a secondary sound signal;

determine a first signal characteristic for the primary sound signal;

determine a second signal characteristic for the secondary sound signal;

determine whether the secondary microphone is obstructed based on the first signal characteristic and second signal characteristic; and

provide a warning indicating that the secondary microphone is obstructed.

37. The computer-readable medium of claim 36 further comprising instructions which when executed by a processor causes the processor to

dynamically select the primary microphone from the plurality of microphones based on which microphone has either the highest signal energy or highest signal-to-noise ratio at a particular period of time.