NOISE BURST ADAPTATION OF SECONDARY PATH ADAPTIVE RESPONSE IN NOISE-CANCELING PERSONAL AUDIO DEVICES

• US 20130301842A1
• Filed: 12/20/2012
• Published: 11/14/2013
• Est. Priority Date: 05/10/2012
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Hendrix, Jon D., Alderson, Jeffrey, Lu, Yang, Miller, Antonio John
• Granted Patent: US 9,082,387 B2
• Time in Patent Office: Days
• US Class Current: 381/71.1
• CPC Class Codes: G10K 11/002 Devices for damping, suppressing, obstructing or conducting sound in acoustic devices G10K1/06 - G10K1/10 take precedence; for electro-mechanical transducers for communication H04R3/002
• CPC Class Codes: G10K 11/178 by electro-acoustically regenerating the original acoustic waves in anti-phase
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17827 Desired external signals, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/108 Communication systems, e.g. where useful sound is kept and noise is cancelled
• CPC Class Codes: G10K 2210/3049 Random noise used, e.g. in model identification

Abstract

A personal audio device, such as a wireless telephone, generates an anti-noise signal from an error microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. The error microphone is also provided proximate the speaker to provide an error signal indicative of the effectiveness of the noise cancellation. A secondary path estimating adaptive filter is used to estimate the electro-acoustical path from the noise canceling circuit through the transducer so that source audio can be removed from the error signal. Noise bursts are injected intermittently and the adaptation of the secondary path estimating adaptive filter controlled, so that the secondary path estimate can be maintained irrespective of the presence and amplitude of the source audio.

Claims

1. A personal audio device, comprising:

a personal audio device housing;

a transducer mounted on the housing for reproducing an audio signal including both source audio for playback to a listener and an anti-noise signal for countering the effects of ambient audio sounds in an acoustic output of the transducer;

an error microphone mounted on the housing in proximity to the transducer for providing an error microphone signal indicative of the acoustic output of the transducer and ambient audio sounds at the transducer;

a noise source for providing a noise signal; and

a processing circuit that generates the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with an error signal, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the source audio and a combiner that removes the source audio from the error microphone signal to provide the error signal, and wherein the processing circuit injects intermittent bursts of noise from the noise source into the secondary path adaptive filter and the audio signal reproduced by the transducer and permits the secondary path adaptive filter to adapt during the intermittent bursts of noise.

2. The personal audio device of claim 1, wherein the processing circuit filters the error signal with a predetermined response to generate the anti-noise signal.

3. The personal audio device of claim 2, further comprising a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds, wherein the processing circuit generates the anti-noise signal from the filtered error signal and the reference signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with the error signal and the reference microphone signal.

4. The personal audio device of claim 1, further comprising a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds, wherein the processing circuit generates the anti-noise signal from the reference signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with the error signal and the reference microphone signal.

5. The personal audio device of claim 4, wherein the processing circuit implements another adaptive filter having a response that generates the anti-noise signal from the reference microphone signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit shapes the response of the another adaptive filter in conformity with the error signal and the reference microphone signal.

6. The personal audio device of claim 5, wherein the processing circuit further controls adaptation of the another adaptive filter and the secondary path adaptive filter such that while an intermittent burst of noise is injected, the another adaptive filter is prevented from adapting and the secondary path adaptive filter is caused to adapt, and once the intermittent burst of noise has terminated, the another adaptive filter is permitted to adapt.

7. The personal audio device of claim 6, wherein the processing circuit further controls adaptation of the another adaptive filter and the secondary path adaptive filter such that once the intermittent burst of noise has terminated, the secondary path adaptive filter is prevented from adapting.

8. The personal audio device of claim 6, wherein the processing circuit determines that one or more coefficients of the another adaptive filter have a rate of change that exceeds a permitted threshold, and wherein the processing circuit injects one or more of the intermittent bursts of noise from the noise source into the secondary path adaptive filter and the audio signal reproduced by the transducer and permits the secondary path adaptive filter to adapt in response to detecting that the one or more coefficients of the another adaptive filter have the rate of change that exceeds the permitted threshold.

9. The personal audio device of claim 6, wherein the processing circuit alters a rate of adapting of the another adaptive filter while the processing circuit injects the intermittent bursts of noise.

10. The personal audio device of claim 6, wherein the processing circuit reduces a rate of adapting of the another adaptive filter while the processing circuit injects the intermittent bursts of noise.

11. The personal audio device of claim 6, wherein the processing circuit only intermittently permits adaptation of the another adaptive filter for predetermined periods after near speech is detected at the personal audio device.

12. The personal audio device of claim 6, wherein the processing circuit injects the one or more of the intermittent bursts of noise in response to determining that a predetermined time period has elapsed since the secondary path adaptive filter has been permitted to adapt.

13. The personal audio device of claim 12, wherein the processing circuit detects whether or not the source audio has sufficient amplitude to permit the secondary path adaptive filter to adapt, and wherein the determining that a predetermined time period has elapsed indicates that the source audio has not had sufficient amplitude to permit the secondary path adaptive filter to adapt for at least the predetermined time period.

14. The personal audio device of claim 1, wherein the processing circuit detects a remote ring signal in the source audio, and wherein the processing circuit injects one or more of the intermittent bursts of noise in response to detecting that the remote ring signal has completed.

15. The personal audio device of claim 14, wherein the processing circuit only injects the one or more of the intermittent bursts of noise after a first remote ring signal of a ring sequence and does not inject any of the intermittent bursts of noise after subsequent remote ring signals of a ring sequence.

16. The personal audio device of claim 1, wherein the processing circuit detects a remote ring signal in the source audio, and wherein the processing circuit injects one or more of the intermittent bursts of noise in response to detecting the remote ring signal and during the remote ring signal.

17. The personal audio device of claim 16, wherein the processing circuit only injects the one or more of the intermittent bursts of noise in response to detecting a first remote ring signal of a ring sequence and does not inject any of the intermittent bursts of noise during or after subsequent remote ring signals of a ring sequence.

18. The personal audio device of claim 1, wherein the processing circuit injects one or more of the intermittent bursts of noise during a telephone conversation in which the personal audio device is participating.

19. A method of countering effects of ambient audio sounds by a personal audio device, the method comprising:

adaptively generating an anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with an error signal;

combining the anti-noise signal with source audio;

providing a result of the combining to a transducer;

measuring an acoustic output of the transducer and the ambient audio sounds with an error microphone;

implementing a secondary path adaptive filter having a secondary path response that shapes the source audio and a combiner that removes the source audio from the error microphone signal to provide the error signal;

injecting intermittent bursts of noise from a noise source into the secondary path adaptive filter and the audio signal reproduced by the transducer; and

permitting the secondary path adaptive filter to adapt during the intermittent bursts of noise.

20. The method of claim 19, wherein the filtering filters the error signal with a predetermined response to generate the anti-noise signal.

21. The method of claim 20, further comprising:

providing a reference microphone signal indicative of the ambient audio sounds; and

generating the anti-noise signal from the filtered error signal and the reference signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with the error signal and the reference microphone signal.

22. The method of claim 19, further comprising:

providing a reference microphone signal indicative of the ambient audio sounds; and

generating the anti-noise signal from the reference signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with the error signal and the reference microphone signal.

23. The method of claim 22, wherein the generating the anti-noise signal is performed by another adaptive filter having a response that generates the anti-noise signal from the reference microphone signal, and wherein the method further comprises shaping the response of the another adaptive filter in conformity with the error signal and the reference microphone signal.

24. The method of claim 23, further comprising controlling adaptation of the another adaptive filter and the secondary path adaptive filter such that while an intermittent burst of noise is injected, the another adaptive filter is prevented from adapting and the secondary path adaptive filter is caused to adapt, and once the intermittent burst of noise has terminated, the another adaptive filter is permitted to adapt.

25. The method of claim 24, wherein the controlling controls the adaptation of the another adaptive filter and the secondary path adaptive filter such that while an intermittent burst of noise is injected, the another adaptive filter is prevented from adapting and the secondary path adaptive filter is caused to adapt, and once the intermittent burst of noise has terminated, the another adaptive filter is permitted to adapt and the secondary path adaptive filter is prevented from adapting.

26. The method of claim 24, further comprising:

determining that one or more coefficients of the another adaptive filter have a rate of change that exceeds a permitted threshold;

injecting one or more of the intermittent bursts of noise from the noise source into the secondary path adaptive filter and the audio signal reproduced by the transducer;

detecting that the one or more coefficients of the another adaptive filter have the rate of change that exceeds the permitted threshold; and

responsive to detecting that the one or more coefficients of the another adaptive filter have the rate of change that exceeds the permitted threshold, permitting the secondary path adaptive filter to adapt.

27. The method of claim 24, further comprising altering a rate of the adapting of the another adaptive filter during the injecting.

28. The method of claim 24, further comprising reducing a rate of the adapting of the another adaptive filter during the injecting.

29. The method of claim 24, wherein the permitting only intermittently permits the adaptation of the another adaptive filter for predetermined periods after near speech is detected at the personal audio device.

30. The method of claim 24, wherein the injecting injects the one or more of the intermittent bursts of noise in response to determining that a predetermined time period has elapsed since the secondary path adaptive filter has been permitted to adapt.

31. The method of claim 30, further comprising detecting whether or not the source audio has sufficient amplitude to permit the secondary path adaptive filter to adapt, and wherein the determining that a predetermined time period has elapsed indicates that the source audio has not had sufficient amplitude to permit the secondary path adaptive filter to adapt for at least the predetermined time period.

32. The method of claim 19, further comprising detecting a remote ring signal in the source audio, and wherein the injecting injects one or more of the intermittent bursts of noise in response to detecting that the remote ring signal has completed.

33. The method of claim 32, wherein the injecting injects the one or more of the intermittent bursts of noise only after a first remote ring signal of a ring sequence and does not inject any of the intermittent bursts of noise after subsequent remote ring signals of a ring sequence.

34. The method of claim 19, further comprising detecting a remote ring signal in the source audio, and wherein the injecting injects one or more of the intermittent bursts of noise in response to detecting the remote ring signal and during the remote ring signal.

35. The method of claim 34, wherein the injecting injects the one or more of the intermittent bursts of noise only in response to detecting a first remote ring signal of a ring sequence and does not inject any of the intermittent bursts of noise during or after subsequent remote ring signals of a ring sequence.

36. The method of claim 19, wherein the injecting injects the one or more of the intermittent bursts of noise during a telephone conversation in which the personal audio device is participating.

37. An integrated circuit for implementing at least a portion of a personal audio device, comprising:

an output for providing an output signal to an output transducer including both source audio for playback to a listener and an anti-noise signal for countering the effects of ambient audio sounds in an acoustic output of the transducer;

an error microphone input for receiving an error microphone signal indicative of the acoustic output of the transducer and ambient audio sounds at the transducer;

a noise source for providing a noise signal; and

a processing circuit that adaptively generates the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with an error signal, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the source audio and a combiner that removes the source audio from the error microphone signal to provide the error signal, and wherein the processing circuit injects intermittent bursts of noise from the noise source into the secondary path adaptive filter and the audio signal reproduced by the transducer and permits the secondary path adaptive filter to adapt during the intermittent bursts of noise.

38. The integrated circuit of claim 37, wherein the processing circuit filters the error signal with a predetermined response to generate the anti-noise signal.

39. The integrated circuit of claim 38, further comprising a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds, wherein the processing circuit generates the anti-noise signal from the filtered error signal and the reference signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with the error signal and the reference microphone signal.

40. The integrated circuit of claim 37, further comprising a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds, wherein the processing circuit generates the anti-noise signal from the reference signal to reduce the presence of the ambient audio sounds heard by the listener in conformity with the error signal and the reference microphone signal.

41. The integrated circuit of claim 40, wherein the processing circuit implements another adaptive filter having a response that generates the anti-noise signal from the reference microphone signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit shapes the response of the another adaptive filter in conformity with the error signal and the reference microphone signal.

42. The integrated circuit of claim 41, wherein the processing circuit further controls adaptation of the another adaptive filter and the secondary path adaptive filter such that while an intermittent burst of noise is injected, the another adaptive filter is prevented from adapting and the secondary path adaptive filter is caused to adapt, and once the intermittent burst of noise has terminated, the another adaptive filter is permitted to adapt.

43. The integrated circuit of claim 42, wherein the processing circuit further controls adaptation of the another adaptive filter and the secondary path adaptive filter such that once the intermittent burst of noise has terminated, the secondary path adaptive filter is prevented from adapting.

44. The integrated circuit of claim 42, wherein the processing circuit determines that one or more coefficients of the another adaptive filter have a rate of change that exceeds a permitted threshold, and wherein the processing circuit injects one or more of the intermittent bursts of noise from the noise source into the secondary path adaptive filter and the audio signal reproduced by the transducer and permits the secondary path adaptive filter to adapt in response to detecting that the one or more coefficients of the another adaptive filter have the rate of change that exceeds the permitted threshold.

45. The integrated circuit of claim 42, wherein the processing circuit alters a rate of adapting of the another adaptive filter while the processing circuit injects the intermittent bursts of noise.

46. The integrated circuit of claim 42, wherein the processing circuit reduces a rate of adapting of the another adaptive filter while the processing circuit injects the intermittent bursts of noise.

47. The integrated circuit of claim 42, wherein the processing circuit only intermittently permits adaptation of the another adaptive filter for predetermined periods after near speech is detected at the personal audio device.

48. The integrated circuit of claim 42, wherein the processing circuit injects the one or more of the intermittent bursts of noise in response to determining that a predetermined time period has elapsed since the secondary path adaptive filter has been permitted to adapt.

49. The integrated circuit of claim 48, wherein the processing circuit detects whether or not the source audio has sufficient amplitude to permit the secondary path adaptive filter to adapt, and wherein the determining that a predetermined time period has elapsed indicates that the source audio has not had sufficient amplitude to permit the secondary path adaptive filter to adapt for at least the predetermined time period.

50. The integrated circuit of claim 37, wherein the processing circuit detects a remote ring signal in the source audio, and wherein the processing circuit injects one or more of the intermittent bursts of noise in response to detecting that the remote ring signal has completed.

51. The integrated circuit of claim 50, wherein the processing circuit only injects the one or more of the intermittent bursts of noise after a first remote ring signal of a ring sequence and does not inject any of the intermittent bursts of noise after subsequent remote ring signals of a ring sequence.

52. The integrated circuit of claim 37, wherein the processing circuit detects a remote ring signal in the source audio, and wherein the processing circuit injects one or more of the intermittent bursts of noise in response to detecting the remote ring signal and during the remote ring signal.

53. The integrated circuit of claim 52, wherein the processing circuit only injects the one or more of the intermittent bursts of noise in response to detecting a first remote ring signal of a ring sequence and does not inject any of the intermittent bursts of noise during or after subsequent remote ring signals of a ring sequence.

54. The integrated circuit of claim 37, wherein the processing circuit injects one or more of the intermittent bursts of noise during a telephone conversation in which the personal audio device is participating.