Sequenced adaptation of anti-noise generator response and secondary path response in an adaptive noise canceling system

• US 9,123,321 B2
• Filed: 12/27/2012
• Issued: 09/01/2015
• 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, Miller, Antonio John, Yong, Chin, Kamath, Gautham Devendra
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): ODUNUKWE, UBACHUKWU A
• Application Number:
  US13/727,718
• Publication Number:
  US 20130301847A1
• Time in Patent Office: 978 Days
• Field of Search: 381/71.1, 381/71.11, 381/71.12, 381/71.14, 455/570, 379/406.08, 379/406.15, 379/406.13, 379/406.09, 379/392, 704/219, 704/226, 704/227, 704/203, 704/201, 708/322
• US Class Current: 1/1
• CPC Class Codes: G10K 11/16 Methods or devices for protecting against, or for damping, noise or other acoustic waves in general G10K11/36 takes precedence
• 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 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17827 Desired external signals, e.g. pass-through audio such as music or speech
• 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 2210/00 Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
• CPC Class Codes: G10K 2210/108 Communication systems, e.g. where useful sound is kept and noise is cancelled
• CPC Class Codes: G10K 2210/3014 Adaptive noise equalizers [ANE], i.e. where part of the unwanted sound is retained
• 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 2210/3028 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: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: H04B 3/237 using two adaptive filters, e.g. for near end and for end echo cancelling

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 to 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. Adaptation of adaptive filters is sequenced so that update of their coefficients does not cause instability or error in the update. A level of the source audio with respect to the ambient audio can be determined to determine whether the system may generate erroneous anti-noise and/or become unstable.

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 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 adaptively generates the anti-noise signal from the reference signal by adapting a first adaptive filter to reduce the presence of the ambient audio sounds heard by the listener in conformity with an error signal and the reference microphone 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 sequences adaptation of the secondary path adaptive filter and the first adaptive filter so that adaptation of a first one of the first adaptive filter or the secondary path adaptive filter is initiated only after adaptation of another one of the first adaptive filter or the secondary path adaptive filter is substantially completed or halted.

2. The personal audio device of claim 1, wherein the processing circuit sequences adaptation of the secondary path adaptive filter and the first adaptive filter such that adaptation of the secondary path adaptive filter is performed prior to adaptation of the first adaptive filter and while adaptation of the first adaptive filter is halted.

3. The personal audio device of claim 2, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter in response to determining that the source audio has characteristics that provide a suitable training signal for adaptation of the secondary path adaptive filter.

4. The personal audio device of claim 3, wherein the processing circuit determines that the source audio contains primarily downlink speech and therefore has characteristics that provide the suitable training signal for adaptation of the secondary path adaptive filter.

5. The personal audio device of claim 2, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter, and injects a training signal that has characteristics that provide a suitable training signal for adaptation of the secondary path adaptive filter into the source audio during adaptation of the secondary path adaptive filter.

6. The personal audio device of claim 5, wherein the training signal is a broadband signal.

7. The personal audio device of claim 2, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter in response to determining that one or more coefficients of the first adaptive filter have a rate of change that exceeds a permitted threshold.

8. The personal audio device of claim 2, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter in response to determining that a predetermined period has elapsed since a previous sequence of adaptation.

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

adaptively generating the anti-noise signal from the reference signal by adapting a first adaptive filter to reduce the presence of ambient audio sounds heard by the listener in conformity with an error signal and the reference microphone signal;

combining the anti-noise signal with source audio;

providing a result of the combining to a transducer;

measuring the ambient audio sounds with a reference microphone;

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; and

sequencing adaptation of the secondary path adaptive filter and the first adaptive filter so that adaptation of a first one of the first adaptive filter or the secondary path adaptive filter is initiated only after adaptation of another one of the first adaptive filter or the secondary path adaptive filter is substantially completed or halted.

10. The method of claim 9, wherein the sequencing sequences the adaptation of the secondary path adaptive filter and the first adaptive filter such that the adaptation of the secondary path adaptive filter is performed prior to adaptation of the first adaptive filter and while the adaptation of the first adaptive filter is halted.

11. The method of claim 10, further comprising:

determining whether the source audio has characteristics that provide a suitable training signal for adaptation of the secondary path adaptive filter; and

responsive to determining that the source audio has characteristics that provide a suitable training signal for adaptation of the secondary path adaptive filter, commencing a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter.

12. The method of claim 11, wherein the determining determines that the source audio contains primarily downlink speech and therefore has characteristics that provide the suitable training signal for adaptation of the secondary path adaptive filter.

13. The method of claim 10, further comprising:

commencing a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter; and

injecting a training signal that has characteristics that provide a suitable training signal for adaptation of the secondary path adaptive filter into the source audio during the adaptation of the secondary path adaptive filter.

14. The method of claim 13, wherein the training signal is a broadband signal.

15. The method of claim 10, further comprising:

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

responsive to determining that the one or more coefficients of the first adaptive filter have a rate of change that exceeds the permitted threshold, commencing a sequence of the adaptation of the secondary path adaptive filter and then the first adaptive filter.

16. The method of claim 10, further comprising:

determining whether a predetermined period has elapsed since a previous sequence of adaptation; and

responsive to determining that the predetermined period has elapsed, commencing a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter.

17. 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;

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 acoustic output of the transducer and the ambient audio sounds at the transducer; and

a processing circuit that adaptively generates the anti-noise signal from the reference signal by adapting a first adaptive filter to reduce the presence of the ambient audio sounds heard by the listener in conformity with an error signal and the reference microphone 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 sequences adaptation of the secondary path adaptive filter and the first adaptive filter so that adaptation of a first one of the first adaptive filter or the secondary path adaptive filter is initiated only after adaptation of another one of the first adaptive filter or the secondary path adaptive filter is substantially completed or halted.

18. The integrated circuit of claim 17, wherein the processing circuit sequences adaptation of the secondary path adaptive filter and the first adaptive filter such that adaptation of the secondary path adaptive filter is performed prior to adaptation of the first adaptive filter and while adaptation of the first adaptive filter is halted.

19. The integrated circuit of claim 18, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter in response to determining that the source audio has characteristics that provide a suitable training signal for adaptation of the secondary path adaptive filter.

20. The integrated circuit of claim 19, wherein the processing circuit determines that the source audio contains primarily downlink speech and therefore has characteristics that provide the suitable training signal for adaptation of the secondary path adaptive filter.

21. The integrated circuit of claim 18, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter, and injects a training signal that has characteristics that provide a suitable training signal for adaptation of the secondary path adaptive filter into the source audio during adaptation of the secondary path adaptive filter.

22. The integrated circuit of claim 21, wherein the training signal is a broadband signal.

23. The integrated circuit of claim 18, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter in response to determining that one or more coefficients of the first adaptive filter have a rate of change that exceeds a permitted threshold.

24. The integrated circuit of claim 18, wherein the processing circuit commences a sequence of adaptation of the secondary path adaptive filter and then the first adaptive filter in response to determining that a predetermined period has elapsed since a previous sequence of adaptation.