CONTINUOUS 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;
a controllable noise source for providing a noise signal; and
a processing circuit that generates the anti-noise signal from the reference 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 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 processing circuit injects noise from the noise generator into the secondary path adaptive filter and the audio signal reproduced by the transducer in place of or in combination with the source audio to cause the secondary path adaptive filter to continue to adapt when the source audio is absent or has reduced amplitude, and wherein the processing circuit controls the controllable noise source in conformity with an output of the secondary path adaptive filter.
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Accused Products
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 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. Noise is injected either continuously and inaudibly below the source audio, or in response to detection that the source audio is low in amplitude, so that the adaptation of the secondary path estimating adaptive filter can be maintained, irrespective of the presence and amplitude of the source audio.
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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; a controllable noise source for providing a noise signal; and a processing circuit that generates the anti-noise signal from the reference 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 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 processing circuit injects noise from the noise generator into the secondary path adaptive filter and the audio signal reproduced by the transducer in place of or in combination with the source audio to cause the secondary path adaptive filter to continue to adapt when the source audio is absent or has reduced amplitude, and wherein the processing circuit controls the controllable noise source in conformity with an output of the secondary path adaptive filter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. 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; 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; combining the anti-noise signal with a source audio signal to generate an audio signal provided to the transducer; shaping a copy of the source audio with a secondary path response; removing the result of the shaping the copy of the source audio from the error microphone signal to produce an error signal indicative of the combined anti-noise and ambient audio sounds delivered to the listener; generating a noise signal; and injecting the noise signal into the secondary path adaptive filter and the audio signal reproduced by the transducer in place of or in combination with the source audio to cause the secondary path adaptive filter to continue to adapt when the source audio is absent or has reduced amplitude, and controlling the controllable noise source in conformity with an output of the secondary path adaptive filter. - 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 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 controllable noise source for providing a noise signal; and a processing circuit that generates the anti-noise signal from the reference 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 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 processing circuit injects noise from the noise generator into the secondary path adaptive filter and the audio signal reproduced by the transducer in place of or in combination with the source audio to cause the secondary path adaptive filter to continue to adapt when the source audio is absent or has reduced amplitude, and wherein the processing circuit controls the controllable noise source in conformity with an output of the secondary path adaptive filter. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification