Adaptive self-calibration of small microphone array by soundfield approximation and frequency domain magnitude equalization

Patent metadata

Field	Value
Publication number	US-9241228-B2
Application number	US-201113339826-A
Country	US
Kind code	B2
Filing date	Dec 29, 2011
Priority date	Dec 29, 2011
Publication date	Jan 19, 2016
Grant date	Jan 19, 2016

Abstract

Methods and apparatus for self-calibration of small-microphone arrays are described. In one embodiment, self-calibration is based upon a mathematical approximation for which a detected response by one microphone should approximately equal a combined response from plural microphones in the array. In a second embodiment, self-calibration is based upon matching gains in each of a plurality of Bark frequency bands, and applying the matched gains to frequency domain microphone signals such that the magnitude response of all the microphones in the array approximates an average magnitude response for the array. The methods and apparatus may be implemented in hearing aids or small audio devices and used to mitigate adverse aging and mechanical effects on acoustic performance of small-microphone arrays in these systems.

First claim

What is claimed is:

1. An adaptive self-calibrating small microphone array comprising:
a plurality of microphones disposed in a two-dimensional or three-dimensional configuration;
a reference microphone; and
a signal processor configured to
associate a respective delay to responses from the plurality of microphones based on a spatial relationship of a respective microphone to the reference microphone,
combine the responses from the plurality of microphones to form a combined response based on the respective delay, wherein the combined response is a mathematical approximation to a reference response, and
compare the combined response to the reference response from the reference microphone.

2. The microphone array of claim 1 , wherein the respective delay is based upon an approximation of a phase relationship for at least one of the plurality of microphones.

3. The microphone array of claim 1 , wherein the signal processor comprises:
a combiner for combining the plural microphone responses;
a plurality of adaptive filters, each configured to receive an output from one of the plurality of microphones and provide a microphone response to the combiner; and
a comparison unit configured to receive an output from the combiner for comparison with the reference response.

4. The microphone array of claim 3 disposed in a hearing aid.

5. The microphone array of claim 3 disposed in a hand-held portable electronic device.

6. The microphone array of claim 3 wherein a spacing between any two microphones in the array is less than about 2 millimeters.

7. The microphone array of claim 3 , wherein an output from the comparison unit is fed back to at least one of the adaptive filters.

8. The microphone array of claim 3 comprising a delay element configured to delay a signal from one of the plurality of microphones.

9. The microphone array of claim 3 , wherein the comparison unit is configured to determine a difference between the combined response and the reference response and provide a signal representative of the difference to the plurality of adaptive filters.

10. The microphone array of claim 3 , wherein each adaptive filter is configured to compensate a respective received output responsive to feedback from the comparison unit to equalize the combined response and the reference response.

11. The microphone array of claim 1 , wherein the reference response is obtained from the reference microphone that is one of the microphones in the directional microphone array.

12. The microphone array of claim 1 , wherein the signal processor is configured to repeatedly execute the combining and comparing on an automated basis to compensate for variations in the microphone responses due to aging of the microphones or mechanical factors affecting acoustic responses of the microphones.

13. A method for compensating microphone responses for a directional microphone array system, the method comprising:
associating a respective delay to responses from a plurality of microphones of the directional array based on a spatial relationship of a respective microphone to a reference microphone;
combining a plurality of microphone responses from the plurality of microphones of the directional microphone array to form a combined response based on the respective delay, wherein the combining is such that the combined response mathematically approximates a reference response; and
comparing the combined response to the reference response.

14. The method of claim 13 , wherein the respective delay is based upon an approximation of a phase relationship for at least one of the plurality of microphones.

15. The method of claim 13 , wherein the reference response is obtained from a reference microphone that is one of the microphones in the directional microphone array.

16. The method of claim 13 , wherein the combining and comparing is carried out by a signal processor coupled to the plurality of microphones.

17. The method of claim 13 , wherein the plurality of microphones are arranged in a two-dimensional or three-dimensional configuration.

18. The method of claim 13 , further comprising obtaining the reference response from a data storage device or measuring the reference response from a reference microphone included with the directional microphone array.

19. The method of claim 13 , further comprising repeatedly and automatically executing the combining and comparing to compensate for variations in the microphone responses due to aging of the microphones or mechanical factors affecting acoustic responses of the microphones.

20. The method of claim 13 , wherein the comparing comprises calculating a difference between the combined response and the reference response to produce an error signal.

21. The method of claim 20 , further comprising:
compensating a signal from at least one of the plural microphones responsive to the error signal to equalize the combined response and the reference response.

22. The method of claim 21 , further comprising calculating an amount of compensation based upon the magnitude of the error signal.

23. The method of claim 21 , wherein the compensating comprises adaptively filtering a response from the at least one of the plurality of microphones.

24. The method of claim 21 , wherein the compensating comprises computing filter coefficients for an adaptive filter coupled to the at least one of the plurality of microphones and providing the computed filter coefficients to the adaptive filter.

Assignees

• Ng Samuel Samsudin
• Karthik Muralidhar
• George Sapna
• St Microelectronics Asia

Inventors

• Ng Samuel Samsudin
• Karthik Muralidhar
• George Sapna

Classifications

• H04R3/005

  for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407) · CPC title

• H04R29/006 Primary

  Microphone matching · CPC title