Coordinated gain control in adaptive noise cancellation (ANC) for earspeakers

• US 9,226,068 B2
• Filed: 03/12/2015
• Issued: 12/29/2015
• Est. Priority Date: 04/26/2012
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Hendrix, Jon D., Alderson, Jeffrey
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): SUTHERS, DOUGLAS JOHN
• Application Number:
  US14/656,124
• Publication Number:
  US 20150189434A1
• Time in Patent Office: 292 Days
• Field of Search: 381/71.1, 381/71.2, 381/71.6, 381/71.11, 381/71.12, 381/71.8, 381/94.1, 381/58, 381/74, 381/122
• US Class Current: 1/1
• CPC Class Codes: G10K 11/175 using interference effects; Masking sound
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17835 using detection of abnormal input signals
• 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 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/30391 Resetting of the filter parameters or changing the algorithm according to prevailing conditions
• CPC Class Codes: G10K 2210/3055 Transfer function of the acoustic system
• 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 2460/01 Hearing devices using active noise cancellation
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits

Abstract

A personal audio device including earspeakers, includes an adaptive noise canceling (ANC) circuit that adaptively generates an anti-noise signal for each earspeaker from at least one microphone signal that measures the ambient audio, and the anti-noise signals are combined with source audio to provide outputs for the earspeakers. The anti-noise signals cause cancellation of ambient audio sounds at the respective earspeakers. A processing circuit uses the microphone signal(s) to generate the anti-noise signals, which can be generated by adaptive filters. The processing circuit controls adaptation of the adaptive filters such that when the processing circuit detects that either of the earspeakers are off-ear, a gain applied to the anti-noise signals is reduced.

Claims

1. A personal audio system, comprising:

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

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

at least one microphone for providing at least one microphone signal indicative of the ambient audio sounds; and

a processing circuit that generates the first anti-noise signal from the at least one microphone signal using a first adaptive filter to reduce the presence of the ambient audio sounds at the first earspeaker in conformity with the at least one microphone signal, wherein the processing circuit generates the second anti-noise signal from the at least one microphone signal using a second adaptive filter to reduce the presence of the ambient audio sounds at the second earspeaker in conformity with the at least one microphone signal, wherein the processing circuit determines a first degree of coupling between the first earspeaker and an ear of the listener and determines a second degree of coupling between the second earspeaker and another ear of the listener, and wherein the processing circuit reduces a gain of both the first adaptive filter and the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener or that the second degree of coupling indicates that the second earspeaker is loosely coupled to the other ear of the listener.

2. The personal audio system of claim 1, wherein the at least one microphone comprises a first microphone mounted on a housing of the first earspeaker and a second microphone mounted on a housing of the second earspeaker, wherein the processing circuit generates the first anti-noise signal from the first microphone, and wherein the processing circuit generates the second anti-noise signal from the second microphone.

3. The personal audio system of claim 1, wherein the processing circuit further halts adaptation of the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener.

4. The personal audio system of claim 3, wherein the processing circuit further reduces a gain of a response of the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener.

5. The personal audio system of claim 1, wherein the processing circuit detects clipping in a first audio path including the first adaptive filter and in a second audio path including the second adaptive filter, and wherein the processing circuit takes action on adaptation of both of the first adaptive filter and the second adaptive filter in response to detecting clipping in either of the first audio path or the second audio path.

6. The personal audio system of claim 5, wherein the processing circuit takes action on the second adaptive filter for a longer period of time than taking action on the first adaptive filter in response to detecting clipping in the first audio path.

7. The personal audio system of claim 1, wherein the processing circuit detects that the ambient audio sounds arriving at the first microphone have exceeded a predetermined amplitude threshold, and in response to detecting that ambient audio sounds have exceeded the predetermined amplitude threshold, the processing circuit halts adaptation of both the first adaptive filter and the second adaptive filter.

8. The personal audio system of claim 1, wherein the processing circuit detects scratching on a first housing of the first earspeaker or wind noise at the first earspeaker and does not detect scratching on a second housing of the second earspeaker or wind noise at the second earspeaker, and in response to detecting scratching on the first housing of the first earspeaker or wind noise at the first earspeaker, mutes the first anti-noise signal and halts adaptation of the first adaptive filter and does not mute the second anti-noise signal.

9. The personal audio system of claim 8, wherein the processing circuit, in response to detecting scratching on the first housing of the first earspeaker or wind noise at the first earspeaker, reduces a gain of the second adaptive filter.

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

first generating a first anti-noise signal from at least one microphone signal using a first adaptive filter to reduce the presence of the ambient audio sounds at a first earspeaker in conformity with the at least one microphone signal;

second generating a second anti-noise signal from the at least one microphone signal using a second adaptive filter to reduce the presence of the ambient audio sounds at a second earspeaker in conformity with the at least one microphone signal;

determining a first degree of coupling between the first earspeaker and an ear of the listener;

determining a second degree of coupling between the second earspeaker and another ear of the listener; and

responsive to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener or that the second degree of coupling indicates that the second earspeaker is loosely coupled to the other ear of the listener, reducing a gain of both the first adaptive filter and the second adaptive filter.

11. The method of claim 10, wherein the at least one microphone comprises a first microphone mounted on a housing of the first earspeaker and a second microphone mounted on a housing of the second earspeaker, wherein the first generating generates the first anti-noise signal from the first microphone, and wherein the second generating generates the second anti-noise signal from the second microphone.

12. The method of claim 10, further comprising

halting adaptation of the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener.

13. The method of claim 12, further comprising reducing a gain of a response of the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener.

14. The method of claim 10, further comprising:

detecting clipping in a first audio path including the first adaptive filter and in a second audio path including the second adaptive filter; and

taking action on adaptation of both of the first adaptive filter and the second adaptive filter in response to detecting clipping in either of the first audio path or the second audio path.

15. The method of claim 14, wherein the taking action on the second adaptive filter is performed for a longer period of time than the taking action on the first adaptive filter in response to detecting clipping in the first audio path.

16. The method of claim 10, wherein the detecting detects that the ambient audio sounds arriving at the first microphone have exceeded a predetermined amplitude threshold, and wherein the method further comprises, in response to detecting that ambient audio sounds have exceeded the predetermined amplitude threshold, halting adaptation of both the first adaptive filter and the second adaptive filter.

17. The method of claim 10, further comprising:

detecting scratching on a first housing of the first earspeaker or wind noise at the first earspeaker, wherein the detecting does not detect scratching on a second housing of the second earspeaker or wind noise at the second earspeaker; and

in response to detecting scratching on the first housing of the first earspeaker or wind noise at the first earspeaker, muting the first anti-noise signal and halting adaptation of the first adaptive filter while not muting the second anti-noise signal.

18. The method of claim 17, further comprising reducing a gain of the second adaptive filter in response to detecting scratching on the first housing of the first earspeaker or wind noise at the first earspeaker.

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

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

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

at least one microphone input for receiving at least one microphone signal indicative of the ambient audio sounds; and

a processing circuit that generates the first anti-noise signal from the at least one microphone signal using a first adaptive filter to reduce the presence of the ambient audio sounds at the first earspeaker in conformity with the at least one microphone signal, wherein the processing circuit generates the second anti-noise signal from the at least one microphone signal using a second adaptive filter to reduce the presence of the ambient audio sounds at the second earspeaker in conformity with the at least one microphone signal, wherein the processing circuit determines a first degree of coupling between the first earspeaker and an ear of the listener and determines a second degree of coupling between the second earspeaker and another ear of the listener, and wherein the processing circuit reduces a gain of both the first adaptive filter and the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener or that the second degree of coupling indicates that the second earspeaker is loosely coupled to the other ear of the listener.

20. The integrated circuit of claim 19, wherein the at least one microphone signal comprises a first microphone signal provided from a first microphone mounted on a housing of a first earspeaker and a second microphone signal provided from a second microphone mounted on a housing of a second earspeaker, wherein the processing circuit generates the first anti-noise signal from the first microphone signal, and wherein the processing circuit generates the second anti-noise signal from the second microphone signal.

21. The integrated circuit of claim 20, wherein the processing circuit halts adaptation of the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener.

22. The integrated circuit of claim 21, wherein the processing circuit further reduces a gain of a response of the second adaptive filter in response to detecting that the first degree of coupling indicates that the first earspeaker is loosely coupled to the ear of the listener.

23. The integrated circuit of claim 19, wherein the processing circuit detects clipping in a first audio path including the first adaptive filter and in a second audio path including the second adaptive filter, and wherein the processing circuit takes action on adaptation of both of the first adaptive filter and the second adaptive filter in response to detecting clipping in either of the first audio path or the second audio path.

24. The integrated circuit of claim 23, wherein the processing circuit takes action on the second adaptive filter for a longer period of time than taking action on the first adaptive filter in response to detecting clipping in the first audio path.

25. The integrated circuit of claim 19, wherein the processing circuit detects that the ambient audio sounds arriving at the first microphone have exceeded a predetermined amplitude threshold, and in response to detecting that ambient audio sounds have exceeded the predetermined amplitude threshold, the processing circuit halts adaptation of both the first adaptive filter and the second adaptive filter.

26. The integrated circuit of claim 19, wherein the at least one microphone signal comprises a first microphone signal provided from a first microphone mounted on a housing of a first earspeaker and a second microphone signal provided from a second microphone mounted on a housing of a second earspeaker, wherein the processing circuit detects scratching or wind noise in the first microphone signal and does not detect scratching or wind noise in the second microphone signal, and in response to detecting scratching or wind noise in the first microphone signal, mutes the first anti-noise signal and halts adaptation of the first adaptive filter and does not mute the second anti-noise signal.

27. The integrated circuit of claim 26, wherein the processing circuit, in response to detecting scratching or wind noise in the first microphone signal, reduces a gain of the second adaptive filter.