Echo cancellation

• US 7,272,224 B1
• Filed: 03/03/2003
• Issued: 09/18/2007
• Est. Priority Date: 03/03/2003
• Status: Active Grant

• Current Assignee: Apple Computer Incorporated (Apple Inc.)
• Original Assignee: Apple Inc.
• Inventors: Salsbury, Ryan R., Normile, James Oliver
• Primary Examiner(s): HAROLD, JEFFEREY F
• Application Number:
  US10/379,125
• Time in Patent Office: 1,660 Days
• Field of Search: 379/406.01, 379/406.08, 379/406.14, 379/387.01, 379/390.03, 379/395
• US Class Current: 379/390.03
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

A method, apparatus, system, and signal-bearing medium that in an embodiment determine a degree of correlation between a speaker output signal and a microphone input signal and modulate an adaptive gain of an acoustic echo canceller based on the degree of correlation.

Claims

1. A method comprising:

determining a degree of correlation between a speaker output signal and a microphone input signal; and

modulating an adaptive gain of an acoustic echo canceller based on the degree of correlation,

wherein determining the degree of correlation comprises,

calculating a power spectrum of the microphone input signal and the speaker output signal,

calculating ratios of frequency components in the power spectrum

dividing a number of the ratios that exceed a threshold by a number of discrete frequencies in the power spectrum.

2. The method of claim 1, further comprising:

suspending the modulating when the degree of correlation is less than a threshold.

3. The method of claim 1, wherein modulating the adaptive gain further comprises:

modulating the adaptive gain to be proportional to the degree of correlation.

4. The method of claim 1, wherein the acoustic echo canceller reduces an echo based on modulating the adaptive gain.

5. The method of claim 4, further comprising:

suppressing a residual echo that was not reduced by the acoustic echo canceller.

6. The method of claim 5, wherein suppressing further comprises:

adding noise at a same amplitude and with similar spectral characteristics as the residual echo.

7. The method of claim 1, wherein determining the degree of correlation further comprises:

calculating a frequency transform of the microphone input signal and the speaker output signal.

8. The method of claim 1, further comprising:

resetting the acoustic echo canceller if the adaptive gain is greater than a threshold.

9. The method of claim 1, further comprising:

reducing the adaptive gain if the adaptive gain is greater than a threshold.

10. An apparatus comprising:

means for determining a degree of correlation between a speaker output signal and a microphone input signal; and

means for modulating an adaptive gain of an acoustic echo canceller based on the degree of correlation,

wherein determining means comprises,

means for calculating a power spectrum of a microphone input signal and a speaker output signal;

means for calculating ratios of frequency components in the power spectrum;

means for dividing a number of the ratios that exceed a threshold by a number of discrete frequencies in the power spectrum.

11. The apparatus of claim 10, further comprising:

means for suspending the modulating when the degree of correlation is less than a threshold.

12. The apparatus of claim 10, wherein the means for modulating the adaptive gain further comprises:

means for modulating the adaptive gain to be proportional to the degree of correlation.

13. The apparatus of claim 10, wherein the acoustic echo canceller further comprises:

means for reducing an echo based on the means for modulating the adaptive gain.

14. The apparatus of claim 13, further comprising:

means for suppressing a residual echo that was not reduced by the means for reducing the echo.

15. The apparatus of claim 13, wherein the means for suppressing further comprises:

means for adding noise at a same amplitude and with similar spectral characteristics as the residual echo.

16. The apparatus of claim 10, wherein the means for determining the degree of correlation further comprises:

means for calculating a frequency transform of the microphone input signal and the speaker output signal.

17. The apparatus of claim 10, further comprising:

means for resetting the acoustic echo canceller if the adaptive gain is greater than a threshold.

18. The apparatus of claim 10, further comprising:

means for reducing the adaptive gain if the adaptive gain is greater than a threshold.

19. A signal-bearing medium bearing instructions, wherein the instructions when read and executed perform operations that comprise:

determining a degree of correlation between a speaker output signal and a microphone input signal; and

modulating an adaptive gain of an acoustic echo canceller based on the degree of correlation,

wherein the determining comprises,

calculating a power spectrum of a microphone input signal and a speaker output signal,

calculating ratios of frequency components in the power spectrum,

dividing a number of the ratios that exceed a threshold by a number of discrete frequencies in the power spectrum to generate a correlation coefficient.

20. The signal-bearing medium of claim 19, further comprising:

suspending the modulating when the degree of correlation is less than a threshold.

21. The signal-bearing medium of claim 19, wherein modulating the adaptive gain further comprises:

modulating the adaptive gain to be proportional to the degree of correlation.

22. The signal-bearing medium of claim 19, wherein the acoustic echo canceller reduces an echo based on the modulating the adaptive gain.

23. The signal-bearing medium of claim 22, further comprising:

suppressing a residual echo that was not reduced by the acoustic echo canceller.

24. The signal-bearing medium of claim 23, wherein suppressing further comprises:

adding noise at a same amplitude and with similar spectral characteristics as the residual echo.

25. The signal-bearing medium of claim 19, wherein determining the degree of correlation further comprises:

calculating a frequency transform of the microphone input signal and the speaker output signal.

26. The signal-bearing medium of claim 19, further comprising:

resetting the acoustic echo canceller if the adaptive gain is greater than a threshold.

27. The signal-bearing medium of claim 19, further comprising:

reducing the adaptive gain if the adaptive gain is greater than a threshold.

28. An electronic device comprising:

a processor; and

a storage device bearing instructions, which when executed on the processor cause the electronic device to perform operations that comprise;

determining a degree of correlation between a speaker output signal and a microphone input signal; and

modulating an adaptive gain of an acoustic echo canceller based on the degree of correlation,

wherein the determining comprises,

calculating a power spectrum of a microphone input signal and a speaker output signal,

calculating ratios of frequency components in the power spectrum,

dividing a number of the ratios that exceed a threshold by a number of discrete frequencies in the power spectrum to generate a correlation coefficient.

29. The electronic device of claim 28, wherein the instructions further comprise:

suspending the modulating when the degree of correlation is less than a threshold.

30. The electronic device of claim 28, wherein modulating the adaptive gain further comprises:

modulating the adaptive gain to be proportional to the degree of correlation.

31. The electronic device of claim 28, wherein the acoustic echo canceller reduces an echo based on the modulating the adaptive gain.

32. The electronic device of claim 31, wherein the instructions further comprise:

suppressing a residual echo that was not reduced by the acoustic echo canceller.

33. The electronic device of claim 32, wherein suppressing further comprises:

adding noise at a same amplitude and with similar spectral characteristics as the residual echo.

34. The electronic device of claim 28, wherein determining the degree of correlation further comprises:

calculating a frequency transform of the microphone input signal and the speaker output signal.

35. The electronic device of claim 28, wherein the instructions further comprise:

resetting the acoustic echo canceller if the adaptive gain is greater than a threshold.

36. The electronic device of claim 28, wherein the instructions further comprise:

reducing the adaptive gain if the adaptive gain is greater than a threshold.