SYSTEM AND METHOD FOR ECHO CANCELLATION

• US 20100057454A1
• Filed: 09/04/2008
• Published: 03/04/2010
• Est. Priority Date: 09/04/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc., Curators of the University of Missouri (University of Missouri)
• Original Assignee: Qualcomm, Inc.
• Inventors: Mohammad, Asif Iqbal, Yoo, Heejong, Challa, Deepak, Grant, Steven L.
• Granted Patent: US 8,600,038 B2
• Time in Patent Office: Days
• US Class Current: 704/233
• CPC Class Codes: H04B 3/234 using double talk detection
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

An echo canceller for improved recognition and removal of an echo from a communication device. The echo canceller can dynamically reduce echo using an improved energy estimator and an improved adaptive filter. The improved energy estimator can determine if conversation is in a single talk period or a double talk period based on the combined energy of both the near end background noise and speech. The improved adaptive filter can reduce echo by dynamically changing adaptation speed or step size. In double talk, the adaptive filter(s) can dynamically slow-down or stop adaptation. In single talk, the filter can dynamically increase the speed of adaptation to improve accuracy, or decrease adaptation speed for stability.

Claims

1. A communication device comprising:

an input configured to receive a signal comprising near end background noise, near end speech signals, and far end echo signals;

an estimator module configured to estimate an energy level of the near end background noise and a level of the near end speech signals to determine whether the communication device is in a double talk mode; and

an adaptive filter configured to reduce the echo signals of the near end signal using a variable step size algorithm, wherein the variable step size algorithm dynamically changes a speed of the adaptive filter.

2. The communication device of claim 1, wherein the speed of the adaptive filter is dynamically decreased by dynamically decreasing a step size or by dynamically increasing a regularization parameter.

3. The communication device of claim 1, wherein the variable step size algorithm dynamically decreases the speed of the adaptive filter when converges to a true room response.

4. The communication device of claim 1, wherein the variable step size algorithm dynamically decreases the speed of the adaptive filter when at least one of following occurs:

the communication device is in a double talk period or the adaptive filter is near an actual true room response.

5. The communication device of claim 1, wherein the variable step size algorithm dynamically increases the speed of the adaptive filter when at least one of following occurs:

the signal contains only far end echo signals or the adaptive filter is away from an actual true room response.

6. The communication device of claim 1, wherein the variable step size algorithm dynamically changes a speed of the adaptive filter during echo path changes.

7. The communication device of claim 1, wherein the adaptive filter solves an adaptation control problem during single talk periods and solves the double talk problem during double talk periods.

8. The communication device of claim 1, further comprising filtering without a double talk detection algorithm.

9. The communication device of claim 1, wherein the estimator module configured to estimate an energy level of the near end background noise and a level of the near end speech signals uses equation 7.

10. The communication device of claim 1, wherein the adaptive filter configured to reduce the echo signals of the near end signal using a variable step size algorithm uses the variable step size given by equation 14.

11. The communication device of claim 1, wherein the adaptive filter uses a least mean square (LMS) based methods or variants of LMS.

12. The communication device of claim 1, wherein the estimator module and the adaptive filter operate in the frequency domain or the time domain.

13. The communication device of claim 12, wherein the speed of the adaptive filter is dynamically decreased by dynamically decreasing a step size or by dynamically increasing a regularization parameter.

14. The communication device of claim 12, wherein the variable step size algorithm dynamically decreases the speed of the adaptive filter when converges to a true room response.

15. The communication device of claim 12, wherein the variable step size algorithm dynamically decreases the speed of the adaptive filter when at least one of following occurs:

the communication device is in a double talk period or the adaptive filter is near an actual true room response.

16. The communication device of claim 12, wherein the variable step size algorithm dynamically increases the speed of the adaptive filter when at least one of following occurs:

the signal contains only far end echo signals or the adaptive filter is away from an actual true room response.

17. The communication device of claim 12, wherein the variable step size algorithm dynamically changes a speed of the adaptive filter during echo path changes.

18. The communication device of claim 12, wherein the adaptive filter solves an adaptation control problem during single talk periods and solves the double talk problem during double talk periods.

19. The communication device of claim 12, further comprising filtering without a double talk detection algorithm.

20. The communication device of claim 12, wherein an estimator module configured to estimate an energy level of the near end background noise and a level of the near end speech signals uses equation 7.

21. The communication device of claim 12, wherein an adaptive filter configured to reduce the echo signals of the near end signal using a variable step size algorithm uses the variable step size given by equation 14.

22. The communication device of claim 12, wherein the adaptive filter uses a least mean square (LMS) based methods or variants of LMS.

23. The communication device of claim 1, wherein the communication device comprises one of a cellular telephone or a bluetooth communication device.

24. The communication device of claim 1, wherein the input comprises at least one microphone.

25. A method of reducing echo signals during wireless communication, comprising:

receiving a voice signal comprising near end background noise, near end speech signals, and far end echo signals;

estimating an energy level comprising both the near end background noise and the near end speech signals;

determining whether said wireless communication is in a double talk period based on the estimated energy level; and

reducing said echo signals using a variable step size adaptive filter.

26. The method of claim 25, wherein reducing said echo signals comprises dynamically reducing the speed of the adaptive filter when at least one of following occurs:

the adaptive filter is close to a true room response or when there is double talk.

27. The method of claim 25, wherein reducing said echo signals comprises dynamically decreasing a step size or dynamically increasing a regularization parameter when at least one of following occurs:

the adaptive filter is close to a true room response or when there is double talk.

28. The method of claim 25, further comprising increasing the speed of the adaptive filter when at least one of following occurs:

said wireless communication is not in a double talk period or the adaptive filter estimate is away from a true room response.

29. The method of claim 25, further comprising filtering without a double talk detection algorithm.

30. An echo cancellation module comprising:

an estimator module configured to estimate the energy of a near end sound signal; and

an adaptive filter configured to determine when said sound signal is in a double talk period and in response to said signal being in double talk, reducing an echo in the near end sound signal, wherein the adaptive filter adjusts a variable step size based on the estimated energy.

31. The echo cancellation module of claim 30, wherein the adjustment of the adaptive filter comprises dynamically reducing the variable step size to decrease a speed of the adaptive filter.

32. The echo cancellation module of claim 31, wherein the variable step size is dynamically reduced during double talk.

33. The echo cancellation module of claim 30, wherein the adjustment of the adaptive filter comprises dynamically increasing the variable step size to increase a speed of the adaptive filter.

34. The echo cancellation module of claim 30, further comprising filtering without a double talk detection algorithm.

35. A wireless communication device, comprising:

means for receiving a voice signal comprising near end background noise, near end speech signals, and far end echo signals;

means for estimating an energy level comprising both the near end background noise and the near end speech signals;

means for determining whether said wireless communication is in a double talk period based on the estimated energy level; and

means for reducing said echo signals using a variable step size adaptive filter.

36. The wireless communication device of claim 35, wherein the reducing means comprises dynamically decreasing a speed by dynamically decreasing a step size or by dynamically increasing a regularization parameter.

37. The wireless communication device of claim 35 wherein the reducing means solves an adaptation control problem during single talk periods and solves the double talk problem during double talk periods.

38. An computer storage, comprising instructions that when executed perform the method of:

receiving a voice signal comprising near end background noise, near end speech signals, and far end echo signals;

estimating an energy level comprising both the near end background noise and the near end speech signals;

determining whether said wireless communication is in a double talk period based on the estimated energy level; and

reducing said echo signals using a variable step size adaptive filter.

39. The computer storage of claim 38, further comprising dynamically increasing a speed of the variable step size adaptive filter when at least one of following occurs:

during single talk periods or the adaptive filter is away from an actual true room response.

40. The computer storage of claim 38, further comprising filtering without a double talk detection algorithm.