Interference suppression techniques

• US 7,613,309 B2
• Filed: 11/07/2002
• Issued: 11/03/2009
• Est. Priority Date: 05/10/2000
• Status: Expired due to Fees

• Current Assignee: Carolyn T. Bilger
• Original Assignee: Carolyn T. Bilger
• Inventors: Liu, Chen, Elledge, Mark, Wheeler, Bruce C., Lansing, Charissa R., Feng, Albert S., Bilger, Robert C., Jones, Douglas L., Bilger, legal representative, O'Brien, William D., Lockwood, Michael E.
• Primary Examiner(s): Chin; Vivian
• Assistant Examiner(s): Tran; Con P
• Application Number:
  US10/290,137
• Publication Number:
  US 20030138116A1
• Time in Patent Office: 2,553 Days
• Field of Search: 381/94.1, 381/71.1, 381/313, 381/356, 381/312, 381/92, 381/94.2, 381/94.3, 381/71.6
• US Class Current: 381/94.1
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: H04R 2201/403 Linear arrays of transducers
• CPC Class Codes: H04R 2225/43 Signal processing in hearing aids to enhance the speech intelligibility
• CPC Class Codes: H04R 2430/20 Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic H04R2203/12 takes precedence
• CPC Class Codes: H04R 25/407 Circuits for combining signals of a plurality of transducers
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

System (10) is disclosed including an acoustic sensor array (20) coupled to processor (42). System (10) processes inputs from array (20) to extract a desired acoustic signal through the suppression of interfering signals. The extraction/suppression is performed by modifying the array (20) inputs in the frequency domain with weights selected to minimize variance of the resulting output signal while maintaining unity gain of signals received in the direction of the desired acoustic signal. System (10) may be utilized in hearing aids, voice input devices, surveillance devices, and other applications.

Claims

1. A method, comprising:

operating a hearing aid including a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;

selecting a direction to monitor for acoustic excitation with the hearing aid;

determining a number of sets of signal transform components each providing a frequency domain form of a different one of the sensor signals;

calculating a number of sets of weight values as a function of a correlation of the sets of signal transform components, an adjustment factor, and the direction, the sets of weight values each being calculated to apply to a specific one of the sets of signal transform components; and

weighting each one of the sets of signal transform components with a different one of the sets of weight values before combining the frequency domain form of the sensor signals with one another to provide an output signal representative of the acoustic excitation emanating from the direction.

2. The method of claim 1, wherein the transform components correspond to different frequencies and the adjustment factor has a first value for a first one of the frequencies and second value different than the first value for a second one of the frequencies to control beamwidth.

3. The method of claim 1, wherein the adjustment factor corresponds to correlation length and further comprising determining a number of different correlations with correlation length adaptively changed in accordance with different values for the adjustment factor.

4. The method of claim 1, further comprising:

determining a level of interference; and

adjusting the beamwidth of the hearing aid in response to the level of interference with the adjustment factor.

5. The method of claim 1, further comprising:

determining a rate of change of at least one frequency of at least one of the sensor signals with respect to time; and

adjusting the correlation length in response to the rate of change with the adjustment factor.

6. The method of claim 1, wherein said calculating is performed to minimize output variance.

7. The method of claim 1, further comprising localizing a selected acoustic source relative to a reference as a function of the transform components.

8. A method, comprising:

operating a hearing aid including a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;

providing a set of signal transform components for each of the sensor signals;

calculating a number of weight values as a function of a correlation of the transform components for each of a number different frequencies, said calculating including applying a first beamwidth control value for a first one of the frequencies and a second beamwidth control value for a second one of the frequencies different than the first beamwidth control value; and

weighting the signal transform components with the weight values to provide an output signal.

9. The method of claim 8, further comprising selecting the first beamwidth value and the second beamwidth value to provide a generally constant beamwidth of the hearing aid over a predefined frequency range.

10. The method of claim 8, wherein the first beamwidth value and the second beamwidth value differ in accordance with a difference in an amount of interference at the first one of the frequencies relative to the second one of the frequencies.

11. The method of claim 8, wherein said calculating is performed to minimize output variance.

12. The method of claim 8, further comprising localizing a selected acoustic source relative to a reference as a function of the transform components.

13. A method, comprising:

operating a hearing aid including a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;

providing a plurality of signal transform components for each of the sensor signals;

calculating a first set of weight values as a function of a first correlation of a first number of the signal transform components corresponding to a first correlation length and a second set of weight values as a function of a second correlation of a second number of the signal transform components corresponding to a second correlation length different that the first correlation length; and

generating an output signal as a function of the first weight values and the second weight values.

14. The method of claim 13, wherein the number of sensors is two and the hearing aid has a single, monaural output.

15. The method of claim 13, wherein said calculating is performed to minimize output variance.

16. The method of claim 13, further comprising localizing a selected acoustic source relative to a reference as a function of the transform components.

17. The method of claim 13, wherein the transform components are of a fourier type.

18. A method comprising:

detecting acoustic excitation with a number of acoustic sensors, the acoustic sensors providing a corresponding number of sensor signals;

establishing a set of signal transform components for each of the sensor signals;

as the acoustic source moves relative to the acoustic sensors, tracking location of the acoustic source relative to a reference as a function of the transform components, wherein said tracking includes generating an array with a number of elements each corresponding to a different azimuth and detecting one or more peak values among the elements of the array; and

providing an output signal as a function of the location and a correlation of the transform components.

19. The method of claim 18, wherein the number of sensors is two and said tracking includes determining a phase difference between the sensor signals.

20. The method of claim 18, wherein the reference is a designated axis and the location is provided in the form of an azimuthal direction.

21. The method of claim 18, further comprising adjusting a beamwidth factor relative to frequency.

22. The method of claim 18, further comprising calculating a number of different correlation matrices and adaptively changing correlation length of one of the matrices relative to another of the matrices.

23. The method of claim 18, further comprising steering a direction-indicating vector corresponding to the location.

24. The method of claim 18, wherein said providing include generating the output signal by weighting the transform components to reduce variance of the output signal and provide a predefined gain.

25. An apparatus, comprising:

a first acoustic sensor operable to provide a first sensor signal;

a second acoustic sensor operable to provide a second sensor signal;

a processor operable to generate an output signal representative of acoustic excitation detected with said first acoustic sensor and said second acoustic sensor from a designated direction, said processor including;

means for transforming said first sensor signal to a first number of frequency domain transform components to provide a frequency domain form of said first sensor signal and said second sensor signal to a second number of frequency domain transform components to provide a frequency domain form of said second sensor signal,

means for calculating a first set of weights specific to said frequency domain form of said first sensor signal and a second set of weights specific to said frequency domain form of said second sensor signal; and

means for weighting said first transform components with said first set of weights to provide a corresponding number of first weighted components and said second transform components with said second set of weights to provide a corresponding number of second weighted components as a function of statistical variance of said output signal and a gain constraint for the acoustic excitation from said designated direction,

means for combining each of said first weighted components with a corresponding one of said second weighted components to provide a frequency domain form of said output signal; and

means for providing a time domain form of said output signal from said frequency domain form.

26. The apparatus of claim 25, wherein said processor includes means for steering said designated direction.

27. The apparatus of claim 25, further comprising at least one acoustic output device responsive to said output signal.

28. The apparatus of claim 25, wherein the apparatus is arranged as a hearing aid.

29. The apparatus of claim 25, wherein the apparatus is arranged as a voice input device.

30. The apparatus of claim 25, wherein said processor is operable to localize an acoustic excitation source relative to a reference.

31. The apparatus of claim 25, wherein said processor is operable to track location of an acoustic excitation source relative to an azimuthal plane.

32. The apparatus of claim 25, wherein said processor is operable to adjust a beamwidth control parameter with frequency.

33. The apparatus of claim 25, wherein said processor is operable to calculate a number of different correlation matrices and adaptively adjust correlation length of one or more of the matrices relative to at least one other of the matrices.