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

Patent metadata

Field	Value
Publication number	US-9633646-B2
Application number	US-201514840831-A
Country	US
Kind code	B2
Filing date	Aug 31, 2015
Priority date	Dec 3, 2010
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

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.

First claim

What is claimed is:

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

Assignees

• Cirrus Logic Inc
• Cirrus Logic Inc

Inventors

• Hendrix Jon D
• Abdollahzadeh Milani Ali
• Kwatra Nitin
• Zhou Dayong
• Lu Yang
• Alderson Jeffrey

Classifications

• G10K11/1784 Primary

  Physics · mapped topic

• H04R1/1083

  Reduction of ambient noise (active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06) · CPC title

• G10K2210/3017

  Copy, i.e. whereby an estimated transfer function in one functional block is copied to another block · CPC title

• G10K2210/3216

  Cancellation means disposed in the vicinity of the source · CPC title

• G10K2210/3226

  Sensor details, e.g. for producing a reference or error signal · CPC title