Filter architecture for an adaptive noise canceler in a personal audio device
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; 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, wherein the processing circuit implements a partitioned filter that controls the generation of the anti-noise signal, wherein the filter is partitioned into a first filter portion having a fixed frequency response that is combined with a variable frequency response of a second filter portion, wherein the first filter portion and the second filter portion are coupled in parallel and receive identical inputs, wherein the processing circuit sums an output of the first filter portion and an output of the second filter portion to generate the anti-noise signal, and wherein the processing circuit shapes the spectrum of the anti-noise signal in conformity with the reference microphone signal to minimize the ambient audio sounds heard by the listener.
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Accused Products
Abstract
A personal audio device, such as a wireless telephone, includes an adaptive noise canceling (ANC) circuit that generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cancel ambient audio sounds. A processing circuit implements one or more adaptive filters that control the generation of the anti-noise signal. At least one of the adaptive filters is partitioned into a first portion having a fixed frequency response and a second portion having a variable frequency response. The partitioned filter may be an adaptive filter that generates the anti-noise signal directly from the reference microphone signal. An error microphone may be provided to measure the ambient sounds and transducer output near the transducer, and a secondary path adaptive filter included to generate an error signal from the error microphone signal, which may be partitioned, alone or in combination.
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Citations
36 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; 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, wherein the processing circuit implements a partitioned filter that controls the generation of the anti-noise signal, wherein the filter is partitioned into a first filter portion having a fixed frequency response that is combined with a variable frequency response of a second filter portion, wherein the first filter portion and the second filter portion are coupled in parallel and receive identical inputs, wherein the processing circuit sums an output of the first filter portion and an output of the second filter portion to generate the anti-noise signal, and wherein the processing circuit shapes the spectrum of the anti-noise signal in conformity with the reference microphone signal to minimize the ambient audio sounds heard by the listener. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. 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; adaptively generating an anti-noise signal for countering the effects of ambient audio sounds at an acoustic output of the transducer, to shape the spectrum of the anti-noise signal in conformity with the reference microphone signal to minimize the ambient audio sounds heard by the listener, wherein the adaptively generating controls the generation of the anti-noise signal using a combined response of a first fixed filter response and a second variable filter response, further comprising combining an output of the first fixed filter response and an output of the second variable filter response to yield a combined output, and further comprising cascading the first fixed filter response and the second variable filter response to yield a combined output; and combining the anti-noise signal with a source audio signal to generate an audio signal provided to the transducer. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. 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; 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, wherein the processing circuit implements a partitioned filter that controls the generation of the anti-noise signal, wherein the filter is partitioned into a first filter portion having a fixed frequency response that is combined with a variable frequency response of a second filter portion, wherein the first filter portion and the second filter portion are coupled in parallel and receive identical inputs, wherein the processing circuit sums an output of the first filter portion and an output of the second filter portion to generate the anti-noise signal, and wherein the processing circuit shapes the spectrum of the anti-noise signal in conformity with the reference microphone signal to minimize the ambient audio sounds heard by the listener. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification