AMBIENT NOISE-BASED ADAPTATION OF SECONDARY PATH ADAPTIVE RESPONSE IN NOISE-CANCELING PERSONAL AUDIO DEVICES
First Claim
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 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 controlled by a secondary path coefficient control circuit in conformity with the error signal, wherein the secondary path adaptive filter shapes the source audio with the secondary path response, wherein the processing circuit removes the source audio as shaped by the secondary path response from the error microphone signal to provide the error signal, wherein the processing circuit provides an ambient noise training signal generated from the reference microphone signal to the secondary path adaptive filter to adapt the secondary path response.
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Accused Products
Abstract
An adaptive noise canceller adapts a secondary path modeling response using ambient noise, rather than using another noise source or source audio as a training source. Anti-noise generated from a reference microphone signal using a first adaptive filter is used as the training signal for training the secondary path response. Ambient noise at the error microphone is removed from an error microphone signal, so that only anti-noise remains. A primary path modeling adaptive filter is used to modify the reference microphone signal to generate a source of ambient noise that is correlated with the ambient noise present at the error microphone, which is then subtracted from the error microphone signal to generate the error signal. The primary path modeling adaptive filter is previously adapted by minimizing components of the error microphone signal appearing in an output of the primary path adaptive filter while the anti-noise signal is muted.
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Citations
24 Claims
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1. A personal audio device, comprising:
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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 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 controlled by a secondary path coefficient control circuit in conformity with the error signal, wherein the secondary path adaptive filter shapes the source audio with the secondary path response, wherein the processing circuit removes the source audio as shaped by the secondary path response from the error microphone signal to provide the error signal, wherein the processing circuit provides an ambient noise training signal generated from the reference microphone signal to the secondary path adaptive filter to adapt the secondary path response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of countering effects of ambient audio sounds by a personal audio device, the method comprising:
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adaptively generating an anti-noise signal from a reference microphone 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 a reference microphone signal; combining the anti-noise signal with source audio; providing a result of the combining to a transducer; 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 controlled by a secondary path coefficient control circuit in conformity with the error signal; shaping the source audio with the secondary path response; removing the source audio as shaped by the secondary path response from the error microphone signal to provide the error signal; generating an ambient noise training signal from the reference microphone signal; and selectively providing the ambient noise training signal to the secondary path adaptive filter to adapt the secondary path response. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An integrated circuit for implementing at least a portion of a personal audio device, comprising:
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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; a noise source for providing a noise signal; and a processing circuit that 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 controlled by a secondary path coefficient control circuit in conformity with the error signal, wherein the secondary path adaptive filter shapes the source audio with the secondary path response, wherein the processing circuit removes the source audio as shaped by the secondary path response from the error microphone signal to provide the error signal, wherein the processing circuit provides an ambient noise training signal generated from the reference microphone signal to the secondary path adaptive filter to adapt the secondary path response. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification