Virtual microphone for adaptive noise cancellation in personal audio devices
First Claim
1. A personal audio device comprising:
- a personal audio device housing;
a transducer coupled to the housing for reproducing an audio signal including both a source audio signal 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 coupled to the housing for providing a reference microphone signal indicative of the ambient audio sounds;
an error microphone coupled to 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;
an adaptive filter having a response that generates an anti-noise signal from the reference microphone signal;
one or more filters for modeling an electro-acoustic path of the anti-noise signal from a location of the error microphone to an eardrum of the listener and having a response that generates a filtered reference microphone signal from the reference microphone signal;
one or more filters for modeling an acoustic path of the ambient audio sounds from the location of the error microphone to the eardrum and having a response that generates a synthesized playback corrected error signal based on the error microphone signal, wherein the synthesized playback corrected error signal is indicative of ambient audio sounds present at the eardrum; and
a coefficient control block that shapes the response of the adaptive filter in conformity with the filtered reference microphone signal and the synthesized playback corrected error signal by adapting the response of the adaptive filter to minimize the ambient audio sounds in the synthesized playback corrected error signal.
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Abstract
A processing circuit may implement an adaptive filter having a response that generates an anti-noise signal from a reference microphone signal, one or more filters for modeling an electro-acoustic path of the anti-noise signal from a location of an error microphone to an eardrum of a listener and having a response that generates a filtered reference microphone signal from the reference microphone signal, one or more filters for modeling an acoustic path of ambient audio sounds from the location of the error microphone to the eardrum and having a response that generates a synthesized playback corrected error signal based on the error microphone signal, wherein the synthesized playback corrected error signal is indicative of ambient audio sounds present at the eardrum, and a coefficient control block that shapes the response of the adaptive filter in conformity with the filtered reference microphone signal and the synthesized playback corrected error signal by adapting the response of the adaptive filter to minimize the ambient audio sounds in the synthesized playback corrected error signal.
274 Citations
33 Claims
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1. A personal audio device comprising:
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a personal audio device housing; a transducer coupled to the housing for reproducing an audio signal including both a source audio signal 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 coupled to the housing for providing a reference microphone signal indicative of the ambient audio sounds; an error microphone coupled to 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; an adaptive filter having a response that generates an anti-noise signal from the reference microphone signal; one or more filters for modeling an electro-acoustic path of the anti-noise signal from a location of the error microphone to an eardrum of the listener and having a response that generates a filtered reference microphone signal from the reference microphone signal; one or more filters for modeling an acoustic path of the ambient audio sounds from the location of the error microphone to the eardrum and having a response that generates a synthesized playback corrected error signal based on the error microphone signal, wherein the synthesized playback corrected error signal is indicative of ambient audio sounds present at the eardrum; and a coefficient control block that shapes the response of the adaptive filter in conformity with the filtered reference microphone signal and the synthesized playback corrected error signal by adapting the response of the adaptive filter to minimize the ambient audio sounds in the synthesized playback corrected error signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for canceling ambient audio sounds in the proximity of a drum reference point of a user of a personal audio device, the method comprising:
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receiving a reference microphone signal indicative of the ambient audio sounds; receiving an error microphone signal indicative of an output of a transducer and the ambient audio sounds at the transducer; generating a source audio signal for playback to a listener; generating a filtered reference microphone signal from the reference microphone signal by filtering the reference microphone signal by one or more filters for modeling an electro-acoustic path of the anti-noise signal from a location of the error microphone to an eardrum of the listener; generating a synthesized playback corrected error signal based on the error microphone signal by filtering the error microphone signal by one or more filters for modeling an acoustic path of the ambient audio sounds from the location of the error microphone to the eardrum, wherein the synthesized playback corrected error signal is indicative of ambient audio sounds present at the eardrum; adaptively generating an anti-noise signal from the reference microphone signal, countering the effects of ambient audio sounds at an acoustic output of the transducer, by adapting, in conformity with the filtered reference microphone signal and the synthesized playback corrected error signal, a response of an adaptive filter that filters an output of the reference microphone to minimize the ambient audio sounds in the error microphone signal; and combining the anti-noise signal with the source audio signal to generate an audio signal provided to the transducer. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An integrated circuit comprising:
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an output for providing a signal to a transducer including both a source audio signal for playback to a listener and an anti-noise signal for countering the effect 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; an adaptive filter having a response that generates an anti-noise signal from the reference microphone signal; one or more filters for modeling an electro-acoustic path of the anti-noise signal from a location of the error microphone to an eardrum of the listener and having a response that generates a filtered reference microphone signal from the reference microphone signal; one or more filters for modeling an acoustic path of the ambient audio sounds from the location of the error microphone to the eardrum and having a response that generates a synthesized playback corrected error signal based on the error microphone signal, wherein the synthesized playback corrected error signal is indicative of ambient audio sounds present at the eardrum; and a coefficient control block that shapes the response of the adaptive filter in conformity with the filtered reference microphone signal and the synthesized playback corrected error signal by adapting the response of the adaptive filter to minimize the ambient audio sounds in the synthesized playback corrected error signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification