FREQUENCY AND DIRECTION-DEPENDENT AMBIENT SOUND HANDLING IN PERSONAL AUDIO DEVICES HAVING ADAPTIVE NOISE CANCELLATION (ANC)

• US 20130301846A1
• Filed: 03/04/2013
• Published: 11/14/2013
• Est. Priority Date: 05/10/2012
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Alderson, Jeffrey, Hendrix, Jon D., Zhou, Dayong
• Granted Patent: US 9,319,781 B2
• Time in Patent Office: Days
• US Class Current: 381/71.7
• 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 11/17819 between the output signals and the reference signals, e.g. to prevent howling
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17825 Error signals
• 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 2210/3012 Algorithms
• CPC Class Codes: G10K 2210/30231 Sources, e.g. identifying noisy processes or components
• CPC Class Codes: G10K 2210/3025 Determination of spectrum characteristics, e.g. FFT
• CPC Class Codes: G10K 2210/3028 Filtering, e.g. Kalman filters or special analogue or digital filters
• CPC Class Codes: G10K 2210/30391 Resetting of the filter parameters or changing the algorithm according to prevailing conditions
• CPC Class Codes: G10K 2210/3226 Sensor details, e.g. for producing a reference or error signal
• CPC Class Codes: G10K 2210/503 Diagnostics; Stability; Alarms; Failsafe
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: H04R 3/002 : Damping circuit arrangements for transducers, e.g. motional feedback circuits

Abstract

A personal audio device, such as a wireless telephone, includes noise canceling circuit that adaptively generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. An error microphone may also be provided proximate the speaker to measure the output of the transducer in order to control the adaptation of the anti-noise signal and to estimate an electro-acoustical path from the noise canceling circuit through the transducer. A processing circuit that performs the adaptive noise canceling (ANC) function also detects frequency-dependent characteristics in and/or direction of the ambient sounds and alters adaptation of the noise canceling circuit in response to the detection.

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;

at least one microphone mounted on the housing for providing at least one microphone signal indicative of the ambient audio sounds; 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 the at least one microphone signal using an adaptive filter, wherein the processing circuit detects a frequency-dependent characteristic of one of the at least one microphone signal and alters adaptation of the adaptive filter in conformity with a result of the detection of the frequency-dependent characteristic.

2. The personal audio device of claim 1, wherein the at least one microphone signal includes a reference microphone signal, and wherein the processing circuit generates the anti-noise signal from the reference microphone signal by providing the reference microphone signal to an input of the adaptive filter, and wherein the processing circuit detects the frequency-dependent characteristic of the reference microphone signal.

3. The personal audio device of claim 1, wherein the at least one microphone signal includes a reference microphone signal, and wherein the processing circuit generates the anti-noise signal from the reference microphone signal by providing the reference microphone signal to an input of the adaptive filter, wherein the at least one microphone includes 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 the ambient audio sounds at the transducer, wherein the processing circuit further implements a secondary path 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 an error signal indicative of the combined anti-noise and ambient audio sounds delivered to the listener, and wherein the adaptive filter generates the anti-noise signal in conformity with the error signal and the reference microphone signal.

4. The personal audio device of claim 3, wherein the processing circuit detects the frequency-dependent characteristic of the reference microphone signal.

5. The personal audio device of claim 3, wherein the processing circuit detects the frequency-dependent characteristic of the error microphone signal.

6. The personal audio device of claim 3, wherein the processing circuit further implements a non-adaptive filter having a fixed response for shaping inputs to a coefficient control block of the adaptive filter, so that sensitivity of the adaptation of the adaptive filter is altered at one or more frequencies or in one or more frequency bands by the fixed response, and wherein the altering of the adaptation of the adaptive filter is performed by altering the fixed response of the non-adaptive filter.

7. The personal audio device of claim 6, wherein the processing circuit selects the fixed response from among multiple predetermined frequency responses in conformity with a result of detecting the frequency-dependent characteristic of the at least one microphone signal.

8. The personal audio device of claim 1, wherein the processing circuit detects the frequency-dependent characteristic of one or both of the reference microphone signal and the error microphone signal.

9. The personal audio device of claim 8, wherein the processing circuit detects the frequency-dependent characteristic of both of the reference microphone signal and the error microphone signal and determines a direction of ambient audio sounds causing the frequency-dependent characteristic, and wherein the processing circuit alters adaptation of the adaptive filter selectively in conformity with the direction of the ambient audio sounds.

10. The personal audio device of claim 1, wherein the at least one microphone signal includes a near-speech microphone mounted on the housing for providing a near-speech microphone signal indicative of speech of the listener and the ambient audio sounds, wherein the processing circuit detects the frequency-dependent characteristic of the near-speech microphone signal.

11. The personal audio device of claim 1, wherein the processing circuit detects the frequency-dependent characteristic of the at least one microphone signal by measuring an amplitude of one or more frequencies or frequency bands of the at least one microphone signal.

12. The personal audio device of claim 11, wherein the one or more frequencies or frequency bands are selectable.

13. The personal audio device of claim 11, further comprising:

a headset connector for connecting an external headset; and

a headset type detection circuit for detecting a type of the external headset, and wherein the processing circuit selects the one or more frequencies or frequency bands in conformity with the detected type of the external headset.

14. The personal audio device of claim 1, wherein the processing circuit halts adaptation of the adaptive filter in response to detecting the frequency-dependent characteristic of the at least one microphone signal.

15. The personal audio device of claim 1, wherein the detecting detects whether low-frequency content is present.

16. The personal audio device of claim 1, wherein the detecting detects whether high-frequency content is present.

17. The personal audio device of claim 1, wherein the altering alters a rate of update of a coefficient control block of the adaptive filter.

18. The personal audio device of claim 1, wherein the processing circuit controls a variable portion of a frequency response of the adaptive filter with a leakage characteristic that restores the response of the adaptive filter to a predetermined response at a particular rate of change, and wherein the processing circuit alters the particular rate of change in conformity with a result of the detection of the frequency-dependent characteristic.

19. The personal audio device of claim 1, wherein the processing circuit alters adaptation of the response of the adaptive filter by altering a characteristic of a signal injected to shape a response of the adaptive filter.

20. 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 the at least one microphone signal using an adaptive filter;

combining the anti-noise signal with source audio;

providing a result of the combining to a transducer;

detecting a frequency-dependent characteristic of one of the at least one microphone signal; and

altering adaptation of the adaptive filter in conformity with a result of the detection of the frequency-dependent characteristic.

21. The method of claim 20, wherein the at least one microphone includes a reference microphone for measuring the ambient audio sounds, wherein the at least one microphone signal includes a reference microphone signal generated from an output of the reference microphone, wherein the method further comprises generating the anti-noise signal from the reference microphone signal by providing the reference microphone signal to an input of the adaptive filter, and wherein the detecting detects the frequency-dependent characteristic of the reference microphone signal.

22. The method of claim 20, wherein the at least one microphone includes a reference microphone for measuring the ambient audio sounds and an error microphone for measuring the ambient audio sounds and an acoustic output of the transducer, wherein the at least one microphone signal includes a reference microphone signal generated from an output of the reference microphone and an error microphone signal generated from an output of the error microphone indicative of an acoustic output of the transducer and the ambient audio sounds at the transducer, wherein adaptively generating generates the anti-noise signal from the reference microphone signal and an error signal indicative of the acoustic output of the transducer and the ambient sounds, wherein the method further comprises:

shaping the source audio with a secondary path response provided by a secondary path adaptive filter; and

removing the shaped source audio from the error microphone signal to generate the error signal.

23. The method of claim 22, wherein the detecting detects the frequency-dependent characteristic of the reference microphone signal.

24. The method of claim 22, wherein the detecting detects the frequency-dependent characteristic of the error microphone signal.

25. The method of claim 22, further comprising shaping inputs to a coefficient control block of the adaptive filter with a non-adaptive filter having a fixed response, so that sensitivity of the adaptation of the adaptive filter is altered at one or more frequencies or in one or more frequency bands by the fixed response, and wherein the altering alters the adaptation of the adaptive filter by altering the fixed response of the non-adaptive filter.

26. The method of claim 25, further comprising selecting the fixed response from among multiple predetermined frequency responses in conformity with a result of detecting the frequency-dependent characteristic of the at least one microphone signal.

27. The method of claim 20, wherein the detecting detects the frequency-dependent characteristic of one or both of the reference microphone signal and the error microphone signal.

28. The method of claim 27, wherein the detecting detects the frequency-dependent characteristic of both of the reference microphone signal and the error microphone signal, and wherein the method further comprises determining a direction of ambient audio sounds causing the frequency-dependent characteristic, and wherein the altering alters the adaptation of the adaptive filter selectively in conformity with the determined direction of the ambient audio sounds.

29. The method of claim 20, wherein the at least one microphone includes a near-speech microphone mounted on the housing for providing a near-speech microphone signal indicative of speech of the listener and the ambient audio sounds, and wherein the detecting detects the frequency-dependent characteristic of the near-speech microphone signal.

30. The method of claim 20, wherein the detecting detects the frequency-dependent characteristic of the at least one microphone signal by measuring an amplitude of one or more frequencies or frequency bands of the at least one microphone signal.

31. The method of claim 30, further comprising selecting the one or more frequencies or frequency bands from among multiple predetermined frequencies or frequency bands.

32. The method of claim 30, further comprising:

connecting an external headset to the personal audio device;

detecting a type of the external headset; and

selecting the one or more frequencies or frequency bands in conformity with the detected type of the external headset.

33. The method of claim 20, wherein the halting halts adaptation of the adaptive filter in response to detecting the frequency-dependent characteristic of the at least one microphone signal.

34. The method of claim 20, wherein the detecting detects whether low-frequency content is present.

35. The method of claim 20, wherein the detecting detects whether high-frequency content is present.

36. The method of claim 20, wherein the altering alters a rate of update of a coefficient control block of the adaptive filter.

37. The method of claim 20, further comprising:

controlling a variable portion of a frequency response of the adaptive filter with a leakage characteristic that restores the response of the adaptive filter to a predetermined response at a particular rate of change; and

altering the particular rate of change in conformity with a result of the detection of the frequency-dependent characteristic.

38. The method of claim 20, wherein the altering alters adaptation of the response of the adaptive filter by altering a characteristic of a signal injected to shape a response of the adaptive filter.

39. 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;

at least one microphone input for receiving at least one microphone signal indicative of the ambient audio sounds; 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 the at least one microphone signal using an adaptive filter, wherein the processing circuit detects a frequency-dependent characteristic of one of the at least one microphone signal and alters adaptation of the adaptive filter in conformity with a result of the detection of the frequency-dependent characteristic.

40. The integrated circuit of claim 39, wherein the at least one microphone signal includes a reference microphone signal indicative of the ambient audio sounds, wherein the processing circuit generates the anti-noise signal from the reference microphone signal by providing the reference microphone signal to an input of the adaptive filter, and wherein the processing circuit detects the frequency-dependent characteristic of the reference microphone signal.

41. The integrated circuit of claim 39, wherein the at least one microphone signal includes a reference microphone signal indicative of the ambient audio sounds and an error microphone signal indicative of the ambient audio sounds and an acoustic output of the transducer, wherein the processing circuit generates the anti-noise signal from the reference microphone signal by providing the reference microphone signal to an input of the adaptive filter, wherein the processing circuit further implements a secondary path 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 an error signal indicative of the combined anti-noise and ambient audio sounds delivered to the listener, and wherein the adaptive filter generates the anti-noise signal in conformity with the error signal and the reference microphone signal.

42. The integrated circuit of claim 41, wherein the processing circuit detects the frequency-dependent characteristic of the reference microphone signal.

43. The integrated circuit of claim 41, wherein the processing circuit detects the frequency-dependent characteristic of the error microphone signal.

44. The integrated circuit of claim 41, wherein the processing circuit further implements a non-adaptive filter having a fixed response for shaping inputs to a coefficient control block of the adaptive filter, so that sensitivity of the adaptation of the adaptive filter is altered at one or more frequencies or in one or more frequency bands by the fixed response, and wherein the altering of the adaptation of the adaptive filter is performed by altering the fixed response of the non-adaptive filter.

45. The integrated circuit of claim 44, wherein the processing circuit selects the fixed response from among multiple predetermined frequency responses in conformity with a result of detecting the frequency-dependent characteristic of the at least one microphone signal.

46. The integrated circuit of claim 39, wherein the processing circuit detects the frequency-dependent characteristic of one or both of the reference microphone signal and the error microphone signal.

47. The integrated circuit of claim 46, wherein the processing circuit detects the frequency-dependent characteristic of both of the reference microphone signal and the error microphone signal and determines a direction of ambient audio sounds causing the frequency-dependent characteristic, and wherein the processing circuit alters adaptation of the adaptive filter selectively in conformity with the direction of the ambient audio sounds.

48. The integrated circuit of claim 39, wherein the at least one microphone signal includes a near-speech microphone signal indicative of speech of the listener and the ambient audio sounds, wherein the processing circuit detects the frequency-dependent characteristic of the near-speech microphone signal.

49. The integrated circuit of claim 39, wherein the processing circuit detects the frequency-dependent characteristic of the at least one microphone signal by measuring an amplitude of one or more frequencies or frequency bands of the at least one microphone signal.

50. The integrated circuit of claim 49, wherein the one or more frequencies or frequency bands are selectable.

51. The integrated circuit of claim 49, further comprising a headset type detection circuit for detecting a type of an external headset coupled to the output, and wherein the processing circuit selects the one or more frequencies or frequency bands in conformity with the detected type of the external headset.

52. The integrated circuit of claim 39, wherein the processing circuit halts adaptation of the adaptive filter in response to detecting the frequency-dependent characteristic of the at least one microphone signal.

53. The integrated circuit of claim 39, wherein the detecting detects whether low-frequency content is present.

54. The integrated circuit of claim 39, wherein the detecting detects whether high-frequency content is present.

55. The integrated circuit of claim 39, wherein the altering alters a rate of update of a coefficient control block of the adaptive filter.

56. The integrated circuit of claim 39, wherein the processing circuit controls a variable portion of a frequency response of the adaptive filter with a leakage characteristic that restores the response of the adaptive filter to a predetermined response at a particular rate of change, and wherein the processing circuit alters the particular rate of change in conformity with a result of the detection of the frequency-dependent characteristic.

57. The integrated circuit of claim 39, wherein the processing circuit alters adaptation of the response of the adaptive filter by altering a characteristic of a signal injected to shape a response of the adaptive filter.

58. 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;

at least two microphones mounted on the housing for providing at least two microphone signals indicative of the ambient audio sounds; 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 at least one of the at least two microphone signals using an adaptive filter, wherein the processing circuit determines a direction of a detected ambient audio sound from the at least two microphone signals, and wherein the processing circuit alters adaptation of the adaptive filter selectively in conformity with the direction of the detected ambient audio sound.

59. The personal audio device of claim 58, wherein the processing circuit alters adaptation of the response of the adaptive filter by altering a characteristic of a signal injected to shape a response of the adaptive filter.

60. The personal audio device of claim 59, wherein the at least two microphone signals include a reference microphone that generates a reference microphone signal and an error microphone that generates an error microphone signal, wherein the processing circuit generates the anti-noise signal from the reference microphone signal by providing the reference microphone signal to an input of the adaptive filter, wherein the error microphone is mounted on the housing in proximity to the transducer so that the error microphone signal is indicative of the acoustic output of the transducer and the ambient audio sounds at the transducer, wherein the processing circuit further implements a secondary path 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 an error signal indicative of the combined anti-noise and ambient audio sounds delivered to the listener, wherein the adaptive filter generates the anti-noise signal in conformity with the error signal and the reference microphone signal, and wherein the processing circuit determines that the detected ambient audio sound arrived at the error microphone less than a predetermined period of time after arriving at the reference microphone, and in response, alters adaptation of the adaptive filter to de-emphasize higher frequencies in the response of the adaptive filter.

61. The personal audio device of claim 58, wherein the processing circuit alters the adapting by weighting the contribution of each of the at least two microphones in conformity with the direction of the detected ambient sound.

62. The personal audio device of claim 61, wherein the weighting disables a contribution of at least one of the at least two microphones to the determining of the direction of the detected ambient sound.

63. 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 at least one of the at least two microphone signals using an adaptive filter;

combining the anti-noise signal with source audio;

providing a result of the combining to a transducer;

measuring the ambient audio sounds with at least two microphones that provide corresponding at least two microphone signals;

determining a direction of a detected ambient audio sound from the at least two microphone signals; and

altering adaptation of the adaptive filter selectively in conformity with the direction of the detected ambient audio sound.

64. The method of claim 63, wherein the altering alters adaptation of the response of the adaptive filter by altering a characteristic of a signal injected to shape a response of the adaptive filter.

65. The method of claim 64, wherein the at least one microphone includes a reference microphone for measuring the ambient audio sounds and an error microphone for measuring the ambient audio sounds and an acoustic output of the transducer, wherein the at least one microphone signal includes a reference microphone signal generated from an output of the reference microphone and an error microphone signal generated from an output of the error microphone indicative of an acoustic output of the transducer and the ambient audio sounds at the transducer, wherein adaptively generating generates the anti-noise signal from the reference microphone signal and an error signal indicative of the acoustic output of the transducer and the ambient sounds, wherein the method further comprises:

shaping the source audio with a secondary path response provided by a secondary path adaptive filter; and

removing the shaped source audio from the error microphone signal to generate the error signal, and wherein the determining determines that the detected ambient audio sound arrived at the error microphone less than a predetermined period of time after arriving at the reference microphone, and wherein altering alters adaptation of the adaptive filter to de-emphasize higher frequencies in the response of the adaptive filter.

66. The method of claim 63, wherein the altering alters the adapting by weighting the contribution of each of the at least two microphones in conformity with the direction of the detected ambient sound.

67. The method of claim 66, wherein the weighting disables a contribution of at least one of the at least two microphones to the determining of the direction of the detected ambient sound.

68. 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;

at least two microphone inputs for receiving at least two microphone signals indicative of the ambient audio sounds; 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 at least one of the at least two microphone signals using an adaptive filter, wherein the processing circuit determines a direction of a detected ambient audio sound from the at least two microphone signals, and wherein the processing circuit alters adaptation of the adaptive filter selectively in conformity with the direction of the detected ambient audio sound.

69. The integrated circuit of claim 68, wherein the processing circuit alters adaptation of the response of the adaptive filter by altering a characteristic of a signal injected to shape a response of the adaptive filter.

70. The integrated circuit of claim 69, wherein the at least two microphone inputs include a reference microphone input for receiving a reference microphone signal indicative of the ambient audio sounds and an error microphone input for receiving an error microphone signal indicative of the acoustic output of the transducer and the ambient audio sounds at the transducer, wherein the processing circuit generates the anti-noise signal from the reference microphone signal by providing the reference microphone signal to an input of the adaptive filter, wherein the processing circuit further implements a secondary path 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 an error signal indicative of the combined anti-noise and ambient audio sounds delivered to the listener, wherein the adaptive filter generates the anti-noise signal in conformity with the error signal and the reference microphone signal, and wherein the processing circuit determines that the detected ambient audio sound arrived at the error microphone less than a predetermined period of time after arriving at the reference microphone, and in response, alters adaptation of the adaptive filter to de-emphasize higher frequencies in the response of the adaptive filter.

71. The integrated circuit of claim 68, wherein the processing circuit alters the adapting by weighting the contribution of each of the at least two microphones in conformity with the direction of the detected ambient sound.

72. The integrated circuit of claim 71, wherein the weighting disables a contribution of at least one of the at least two microphones to the determining of the direction of the detected ambient sound.