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

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 a response of an adaptive filter that filters an output of the reference microphone;
• 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, a signal due to positive feedback through the reference microphone due to alteration of coupling between the transducer and the reference microphone, or a signal level of the reference microphone signal falling outside of a predetermined range;
• responsive to the detecting, changing the adapting of the at least one adaptive filter independent of the computing of the coefficients that control the response of the adaptive filter, wherein the changing changes the adapting of the adaptive filter by halting the adapting of the at least one of the adaptive filter and muting the anti-noise signal during the ambient audio event.

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, a signal due to positive feedback through the reference microphone due to alteration of coupling between the transducer and the reference microphone, or a signal level of the reference microphone signal falling outside of a predetermined range, wherein the processing circuit changes the adaptation of the adaptive filter by halting the adaptation of the at least one of the adaptive filter, and wherein the processing circuit further mutes the anti-noise signal during the ambient audio event.

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 implements a detector that detects that the anti-noise signal is likely erroneous by detecting variations in the coefficients of the at least one adaptive filter and in response to detecting the variations, removes the anti-noise signal from the audio signal reproduced by the transducer.

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 at least one 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 the anti-noise signal is likely erroneous by detecting variations in the coefficients of the one adaptive filter;
• and
• responsive to the detecting, removing the anti-noise signal from the audio signal reproduced by the transducer.

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 implements a detector that detects that the anti-noise signal is likely erroneous by detecting variations in the coefficients of the at least one adaptive filter and in response to detecting the variations, removes the anti-noise signal from the audio signal reproduced by the transducer.

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;
• 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 an adaptive control of the response of the at least one adaptive filter has a leakage characteristic that restores the response of the at least one adaptive filter to a predetermined response at a particular rate of change, wherein the processing circuit shapes the response of the at least one adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, and wherein the processing circuit changes the leakage characteristic of the at least one adaptive filter in response to detecting that near-end speech is occurring.

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 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 a response of an adaptive filter that filters an output of the reference microphone, wherein an adaptive control of the response of the adaptive filter has a leakage characteristic that restores the response of the adaptive filter to a predetermined response at a particular rate of change;
• combining the anti-noise signal with a source audio signal to generate an audio signal provided to the transducer;
• detecting near-end speech;
• and
• responsive to detecting the near-end speech, changing the leakage characteristic.

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;
• 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 an adaptive control of the response of the at least one adaptive filter has a leakage characteristic that restores the response of the at least one adaptive filter to a predetermined response at a particular rate of change, wherein the processing circuit shapes the response of the at least one adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, and wherein the processing circuit changes the leakage characteristic of the at least one adaptive filter in response to detecting that near-end speech is occurring.