SOURCE AUDIO ACOUSTIC LEAKAGE DETECTION AND MANAGEMENT IN AN ADAPTIVE NOISE CANCELING SYSTEM

• US 20150269926A1
• Filed: 06/09/2015
• Published: 09/24/2015
• 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
• Granted Patent: US 9,773,490 B2
• Time in Patent Office: Days
• 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. A level of the source audio with respect to the ambient audio is 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 an anti-noise signal for countering effects of ambient audio sounds in an acoustic output of the output transducer;

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

a processing circuit within the housing that adaptively generates the anti-noise signal from the reference microphone signal such that the anti-noise signal causes substantial cancellation of the ambient audio sounds, wherein the processing circuit, in response to determining that an amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to an amplitude of the ambient audio sounds, takes action to prevent improper generation of the anti-noise signal.

2. The personal audio device of claim 1, further comprising an error microphone mounted on the housing that generates an error microphone signal indicative of the acoustic output of the output transducer and the ambient audio sounds at the output transducer, wherein the processing circuit further generates the anti-noise signal in conformity with an error 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 taking action comprises 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.

3. The personal audio device of claim 2, 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, and wherein the sequencing of the adaptation is performed in response to the processing circuit determining that the amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to the amplitude of the ambient audio sounds.

4. The personal audio device of claim 2, wherein the processing circuit determining that an amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to an amplitude of the ambient audio sounds by comparing an amplitude of the source audio to a threshold value.

5. The personal audio device of claim 4, wherein the processing circuit further determines the threshold value from a measurement of a magnitude of the ambient audio sounds.

6. The personal audio device of claim 4, wherein the processing circuit further determines the amplitude of the source audio from a volume setting of the personal audio device.

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

adaptively generating an anti-noise signal from the reference microphone signal with a first adaptive filter such that the anti-noise signal causes substantial cancellation of the ambient audio sounds;

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;

determining whether an amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to an amplitude of the ambient audio sounds; and

responsive to determining that the amplitude of the acoustic leakage of the source audio into the reference microphone is substantial with respect to the amplitude of the ambient audio sounds, taking action to prevent improper generation of the anti-noise signal.

8. The method of claim 7, further comprising:

generating an error microphone signal indicative of the acoustic output of the output transducer and the ambient audio sounds at the output transducer;

generating the anti-noise signal in conformity with an error signal;

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.

9. The method of claim 8, further comprising, responsive to determining that the amplitude of the acoustic leakage of the source audio into the reference microphone is substantial with respect to the amplitude of the ambient audio sounds, sequencing the 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.

10. The method of claim 9, wherein the determining determines that an amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to an amplitude of the ambient audio sounds by comparing an amplitude of the source audio to a threshold value.

11. The method of claim 10, further comprising determining the threshold value from a measurement of a magnitude of the ambient audio sounds.

12. The method of claim 10, wherein the determining determines the amplitude of the source audio from a volume setting of the personal audio device.

13. 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; and

a processing circuit within the housing that adaptively generates the anti-noise signal from the reference microphone signal such that the anti-noise signal causes substantial cancellation of the ambient audio sounds, wherein the processing circuit, in response to determining that an amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to an amplitude of the ambient audio sounds, takes action to prevent improper generation of the anti-noise signal.

14. The integrated circuit of claim 13, further comprising an error microphone input for receiving an error microphone signal indicative of the acoustic output of the output transducer and the ambient audio sounds at the output transducer, wherein the processing circuit further generates the anti-noise signal in conformity with an error 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 taking action comprises 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.

15. The integrated circuit of claim 14, 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, and wherein the sequencing of the adaptation is performed in response to the processing circuit determining that the amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to the amplitude of the ambient audio sounds.

16. The integrated circuit of claim 14, wherein the processing circuit determining that an amplitude of acoustic leakage of the source audio into the reference microphone is substantial with respect to an amplitude of the ambient audio sounds by comparing an amplitude of the source audio to a threshold value.

17. The integrated circuit of claim 16, wherein the processing circuit further determines the threshold value from a measurement of a magnitude of the ambient audio sounds.

18. The integrated circuit of claim 16, wherein the processing circuit further determines the amplitude of the source audio from a volume setting of the personal audio device.