Oversight control of an adaptive noise canceler in a personal audio device

• US 9,633,646 B2
• Filed: 08/31/2015
• Issued: 04/25/2017
• Est. Priority Date: 12/03/2010
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Hendrix, Jon D., Abdollahzadeh Milani, Ali, Kwatra, Nitin, Zhou, Dayong, Lu, Yang, Alderson, Jeffrey
• Primary Examiner(s): CHIN, VIVIAN C
• Assistant Examiner(s): Fahnert, Friedrich W
• Application Number:
  US14/840,831
• Publication Number:
  US 20160063988A1
• Time in Patent Office: 603 Days
• Field of Search: 381 56- 58, 381 712, 381 717, 381 718, 381 7111, 381 731, 381 77, 381 79, 381 91, 381 92, 381 941- 943, 381 949, 381 95- 98, 381122, 381334, 381345, 381 716
• 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 11/17833 by using a self-diagnostic function or a malfunction prevention function, e.g. detecting abnormal output levels
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17855 for improving speed or power requirements
• 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 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/3017 Copy, i.e. whereby an estimated transfer function in one functional block is copied to another block
• CPC Class Codes: G10K 2210/3045 Multiple acoustic inputs, single acoustic output
• CPC Class Codes: G10K 2210/3216 Cancellation means disposed in the vicinity of the source
• CPC Class Codes: G10K 2210/3226 Sensor details, e.g. for producing a reference or error signal
• CPC Class Codes: G10K 2210/504 Calibration
• 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 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's

Abstract

A personal audio device, such as a wireless telephone, includes an adaptive noise canceling (ANC) 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 is also provided proximate the speaker to measure the ambient sounds and transducer output near the transducer, thus providing an indication of the effectiveness of the noise canceling. A processing circuit uses the reference and/or error microphone, optionally along with a microphone provided for capturing near-end speech, to determine whether the ANC circuit is incorrectly adapting or may incorrectly adapt to the instant acoustic environment and/or whether the anti-noise signal may be incorrect and/or disruptive and then take action in the processing circuit to prevent or remedy such conditions.

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;

a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds;

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; and

a processing circuit that implements at least one adaptive filter having a response that generates the anti-noise signal from the reference signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit implements a coefficient control block that shapes the response of the at least one adaptive filter in conformity with the error microphone signal and the reference microphone signal by computing coefficients that determine the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, and wherein the processing circuit detects that an ambient audio event is occurring that could cause the adaptive filter to generate an undesirable component in the anti-noise signal and changes the adapting of the at least one adaptive filter independent of the computing of the coefficients by the coefficient control block, wherein the ambient audio event is wind noise, scratching on the housing of the personal audio device, a substantially tonal ambient sound, or a signal level of the reference microphone signal falling outside of a predetermined range.

2. The personal audio device of claim 1, wherein the processing circuit changes the adaptation of the adaptive filter by halting the adaptation of the at least one of the adaptive filter.

3. The personal audio device of claim 1, wherein the processing circuit mutes the anti-noise signal during the ambient audio event.

4. The personal audio device of claim 1, wherein the processing circuit sets one or more coefficients of the at least one adaptive filter to a predetermined value to remedy disruption of the adapting of the response of the at least one adaptive filter by the ambient audio event.

5. The personal audio device of claim 1, wherein the ambient audio event is a level of the reference microphone signal falling outside of a predetermined range.

6. The personal audio device of claim 1, wherein the ambient audio event is substantially tonal.

7. The personal audio device of claim 1, wherein the ambient audio event is near-end speech.

8. A method of canceling ambient audio sounds in the proximity of a transducer of a personal audio device, the method comprising:

first measuring ambient audio sounds with a reference microphone to produce a reference microphone signal;

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

adaptively generating an anti-noise signal by computing coefficients that control a response of an adaptive filter from a result of the first measuring and the second measuring for countering the effects of ambient audio sounds at an acoustic output of the transducer by adapting the response of the adaptive filter, wherein the adaptive filter filters an output of the reference microphone to generate the anti-noise signal;

combining the anti-noise signal with a source audio signal to generate an audio signal provided to the transducer;

detecting that an ambient audio event is occurring that could cause the adaptive filter to generate an undesirable component in the anti-noise signal, wherein the ambient audio event is wind noise, scratching on a housing of the personal audio device, a substantially tonal ambient sound, or a signal level of the reference microphone signal falling outside of a predetermined range; and

responsive to the detecting, changing the adapting of the at least one adaptive filter independent of the computing of the coefficients.

9. The method of claim 8, wherein the changing changes the adaptation of the adaptive filter by halting the adaptation of the at least one of the adaptive filter.

10. The method of claim 8, further comprising muting the anti-noise signal during the ambient audio event.

11. The method of claim 8, wherein the changing sets one or more coefficients of the at least one adaptive filter to a predetermined value to remedy disruption of the adapting of the response of the at least one adaptive filter by the ambient audio event.

12. The method of claim 8, wherein the ambient audio event is a level of the reference microphone signal falling outside of a predetermined range.

13. The method of claim 8, wherein the ambient audio event is substantially tonal.

14. The method of claim 8, wherein the ambient audio event is near-end speech.

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

an output for providing a signal to a 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;

a reference microphone input for receiving a reference microphone signal indicative of the ambient audio sounds;

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

a processing circuit that implements at least one adaptive filter having a response that generates the anti-noise signal from the reference signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit implements a coefficient control block that shapes the response of the at least one adaptive filter in conformity with the error microphone signal and the reference microphone signal by computing coefficients that determine the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, and wherein the processing circuit detects that an ambient audio event is occurring that could cause the adaptive filter to generate an undesirable component in the anti-noise signal and changes the adapting of the at least one adaptive filter independent of the computing of the coefficients by the coefficient control block, wherein the ambient audio event is wind noise, scratching on a housing of the personal audio device, a substantially tonal ambient sound, or a signal level of the reference microphone signal falling outside of a predetermined range.

16. The integrated circuit of claim 15, wherein the processing circuit changes the adaptation of the adaptive filter by halting the adaptation of the at least one of the adaptive filter.

17. The integrated circuit of claim 15, wherein the processing circuit mutes the anti-noise signal during the ambient audio event.

18. The integrated circuit of claim 15, wherein the processing circuit sets one or more coefficients of the at least one adaptive filter to a predetermined value to remedy disruption of the adapting of the response of the at least one adaptive filter by the ambient audio event.

19. The integrated circuit of claim 15, wherein the ambient audio event is a level of the reference microphone signal falling outside of a predetermined range.

20. The integrated circuit of claim 15, wherein the ambient audio event is substantially tonal.

21. The integrated circuit of claim 15, wherein the ambient audio event is near-end speech.