Sidetone management in an adaptive noise canceling (ANC) system including secondary path modeling
First Claim
1. A wireless telephone, comprising:
- a housing;
a transducer mounted on the housing for reproducing an audio signal including combined downlink audio and sidetone 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 near-speech microphone mounted on the housing for providing a near-speech microphone signal indicative of speech of the listener and the ambient audio sounds; and
a processing circuit that generates the anti-noise signal from the reference microphone signal 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 generates sidetone from a portion of the near-speech microphone signal, wherein the processing circuit combines the downlink audio with the sidetone, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the combined downlink audio and sidetone and a combiner that removes an output of the secondary path adaptive filter from the error microphone signal to provide the error signal, wherein the secondary path adaptive filter is controlled by a secondary path coefficient controller that compares the error signal with the downlink audio and adapts to minimize components of the downlink audio present in the error signal but does not minimize components of the sidetone, so that the anti-noise signal is not affected by the ambient audio sounds present in the near-speech microphone signal.
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Accused Products
Abstract
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 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. Sidetone is injected into the transducer output, but is not provided to the coefficient control of the secondary path estimating adaptive filter, so that the ambient noise present in the near-end speech microphone signal, and thus present in the sidetone information, does not destabilize the ANC circuit or otherwise cause improper generation of the anti-noise signal.
276 Citations
21 Claims
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1. A wireless telephone, comprising:
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a housing; a transducer mounted on the housing for reproducing an audio signal including combined downlink audio and sidetone 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 near-speech microphone mounted on the housing for providing a near-speech microphone signal indicative of speech of the listener and the ambient audio sounds; and a processing circuit that generates the anti-noise signal from the reference microphone signal 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 generates sidetone from a portion of the near-speech microphone signal, wherein the processing circuit combines the downlink audio with the sidetone, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the combined downlink audio and sidetone and a combiner that removes an output of the secondary path adaptive filter from the error microphone signal to provide the error signal, wherein the secondary path adaptive filter is controlled by a secondary path coefficient controller that compares the error signal with the downlink audio and adapts to minimize components of the downlink audio present in the error signal but does not minimize components of the sidetone, so that the anti-noise signal is not affected by the ambient audio sounds present in the near-speech microphone signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of canceling ambient audio sounds in the proximity of a transducer of a personal audio device, the method comprising:
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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; third measuring near-end speech and the ambient audio sounds with a near-speech microphone to produce a near-speech microphone signal; adaptively generating an anti-noise signal from a result of the first measuring, the second measuring and the third measuring, for countering the effects of ambient audio sounds at an acoustic output of the transducer; first combining the anti-noise signal with a source audio signal and a portion of the near-speech microphone signal to generate an audio signal provided to the transducer; shaping a result of the first combining with a secondary path response; removing the result of the shaping the result of the first combining with the error microphone signal to produce an error signal indicative of the combined anti-noise and ambient audio sounds delivered to the listener; controlling the secondary path response by comparing the error signal with the downlink audio to generate coefficients of the secondary path response; and adapting the secondary response to minimize components of the source audio present in the error signal, but so as not to minimize components of the near-speech microphone signal, so that the anti-noise signal is not affected by the ambient audio sounds present in the near-speech microphone signal. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. An integrated circuit for implementing at least a portion of a personal audio device, comprising:
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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 acoustic output of the transducer and the ambient audio sounds at the transducer; a near-speech microphone input for providing a near-speech microphone signal indicative of speech of the listener and the ambient audio sounds; and a processing circuit that generates the anti-noise signal from the reference microphone signal 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 generates sidetone from a portion of the near-speech microphone signal, wherein the processing circuit combines the downlink audio with the sidetone, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the combined downlink audio and sidetone and a combiner that removes an output of the secondary path adaptive filter from the error microphone signal to provide the error signal, wherein the secondary path adaptive filter is controlled by a secondary path coefficient controller that compares the error signal with the downlink audio and adapts to minimize components of the downlink audio present in the error signal but does not minimize components of the sidetone, so that the anti-noise signal is not affected by the ambient audio sounds present in the near-speech microphone signal. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification