Adaptive noise canceling architecture for 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;
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 processing circuit that implements an adaptive filter having a response 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 coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, wherein a first sample rate of the adaptive filter is substantially higher than a second sample rate at which the coefficient control block operates, wherein the source audio has a sample rate equal to or less than the second sample rate;
an interpolator included in the processing circuit that converts the source audio to the first sample rate; and
a combiner included in the processing circuit that combines the anti-noise signal and an output of the interpolator to generate the audio signal at the first sample rate.
2 Assignments
0 Petitions
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 that measures the ambient audio and an error microphone signal that measures the output of an output transducer plus any ambient audio at that location and injects the anti-noise signal at the transducer output to cause cancellation of ambient audio sounds. A processing circuit uses the reference and error microphone to generate the anti-noise signal, which can be generated by an adaptive filter operating at a multiple of the ANC coefficient update rate. Downlink audio can be combined with the high data rate anti-noise signal by interpolation. High-pass filters in the control paths reduce DC offset in the ANC circuits, and ANC coefficient adaptation can be halted when downlink audio is not detected.
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Citations
27 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 processing circuit that implements an adaptive filter having a response 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 coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, wherein a first sample rate of the adaptive filter is substantially higher than a second sample rate at which the coefficient control block operates, wherein the source audio has a sample rate equal to or less than the second sample rate; an interpolator included in the processing circuit that converts the source audio to the first sample rate; and a combiner included in the processing circuit that combines the anti-noise signal and an output of the interpolator to generate the audio signal at the first sample rate. - View Dependent Claims (2)
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3. 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 a result of the second measuring for countering the effects of the ambient audio sounds at an acoustic output of the transducer by adapting a response of an adaptive filter that filters an output of the reference microphone; combining the anti-noise signal with a source audio signal to generate an audio signal provided to the transducer, wherein the anti-noise signal is generated at a first sample rate that is substantially higher than a second sample rate of a coefficient control of the adaptive filter, wherein the source audio has a sample rate equal to or less than the second sample rate; converting the source audio to the first sample rate by interpolation; and combining the anti-noise signal and a result of the converting to generate the audio signal at the first sample rate. - View Dependent Claims (4)
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5. 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 processing circuit that implements an adaptive filter having a response 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 coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, wherein a first sample rate of the adaptive filter is substantially higher than a second sample rate at which the coefficient control block operates, wherein the source audio has a sample rate equal to or less than the second sample rate; an interpolator included in the processing circuit that converts the source audio to the first sample rate; and a combiner included in the processing circuit that combines the anti-noise signal and an output of the interpolator to generate the audio signal at the first sample rate. - View Dependent Claims (6)
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7. A personal audio device, comprising:
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a personal audio device housing; an audio source having an output providing source audio for playback to a listener; a transducer mounted on the housing for reproducing an audio signal; a combiner for combining the source audio and an anti-noise signal for countering the effects of ambient audio sounds in an acoustic output of the transducer, to generate the audio signal; 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 implements an adaptive filter having a response 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 coefficient control block that shapes the response of the adaptive filter by adjusting coefficients that determine the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal to minimize the ambient audio sounds at the error microphone, wherein the processing circuit detects whether or not the source audio is present at the output of the audio source, and in response to detecting that the source audio is not present, halts adjustment of the coefficients while continuing to generate the anti-noise signal. - View Dependent Claims (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; providing source audio from an audio source; 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 a result of the second measuring for countering the effects of ambient audio sounds at an acoustic output of the transducer by adjusting coefficients that determine the response of an adaptive filter that filters an output of the reference microphone; combining the source audio with the anti-noise signal; reproducing the combined source audio and anti-noise signal by the transducer; detecting whether or not the source audio is present at an output of the audio source; responsive to detecting that the source audio is not present, halting adjustment of the coefficients while continuing to generate the anti-noise signal. - View Dependent Claims (10)
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11. An integrated circuit for implementing at least a portion of a personal audio device, comprising:
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an audio source having an output providing source audio for playback to a listener; a combiner for combining the source audio and an anti-noise signal for countering the effects of ambient audio sounds in an acoustic output of a transducer, to generate an audio signal; an output for providing the audio signal to 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; and a processing circuit that implements an adaptive filter having a response 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 coefficient control block that shapes the response of the adaptive filter by adjusting coefficients that determine the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal to minimize the ambient audio sounds at the error microphone, wherein the processing circuit detects whether or not the source audio is present at the output of the audio source, and in response to detecting that the source audio is not present, halts adjustment of the coefficients while continuing to generate the anti-noise signal. - View Dependent Claims (12)
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13. 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; a first analog-to-digital converter for converting the reference microphone signal to a reference microphone digital representation; 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 second analog-to-digital converter for converting the error microphone signal to an error microphone digital representation; and a processing circuit that implements an adaptive filter having a response that generates the anti-noise signal from the reference microphone digital representation to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit implements a coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone digital representation and the reference microphone digital representation by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, wherein the processing circuit further implements a first digital filter having a first high-pass characteristic coupled between the first analog-to-digital converter and an input to the adaptive filter from which the anti-noise signal is generated for removing first DC components from the input to the adaptive filter, and wherein the processing circuit further implements a second digital filter having a second high-pass characteristic that differs from the first high-pass characteristic coupled between the first analog-to-digital converter and the coefficient control block for removing second DC components from a first input to the coefficient control block. - View Dependent Claims (14, 15)
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16. 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; first converting a result of the first measuring to a first digital representation; second measuring an output of the transducer and the ambient audio sounds at the transducer with an error microphone; second converting a result of the second measuring to a second digital representation; first filtering the first digital representation with a first digital high-pass filter; second filtering the first digital representation with a second digital high-pass filter having a response that differs from a response of the first digital high-pass filter; and adaptively generating an anti-noise signal from a result of the first filtering for countering the effects of ambient audio sounds at an acoustic output of the transducer by adapting a response of an adaptive filter that filters the result of the first filtering, wherein the first filtering acts to remove first DC components from an input to the adaptive filter, and wherein a response of the adaptive filter is adjusted according to a coefficient control block that receives a result of the second filtering and the second digital representation, and wherein the second filtering acts to remove first DC components from a first input to a coefficient control block that controls the adaptive filter. - View Dependent Claims (17, 18)
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19. 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; a first analog-to-digital converter for converting the reference microphone signal to a reference microphone digital representation; 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; and a second analog-to-digital converter for converting the error microphone signal to an error microphone digital representation; and a processing circuit that implements an adaptive filter having a response that generates the anti-noise signal from the reference microphone digital representation to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit implements a coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone digital representation and the reference microphone digital representation by adapting the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, wherein the processing circuit further implements a first digital filter having a first high-pass characteristic coupled between the first analog-to-digital converter and an input to the adaptive filter from which the anti-noise signal is generated for removing first DC components from the input to the adaptive filter, and wherein the processing circuit further implements a second digital filter having a second high-pass characteristic that differs from the first high-pass characteristic coupled between the first analog-to-digital converter and the coefficient control block for removing second DC components from a first input to the coefficient control block. - View Dependent Claims (20, 21)
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22. 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; a first analog-to-digital converter for converting the reference microphone signal to a first reference microphone signal digital representation at a first sample rate; a first sigma-delta quantizer that quantizes the first digital representation at the first sample rate to generate a lowered resolution second reference microphone signal digital representation at the first sample rate; and a processing circuit that implements an adaptive filter having a response that generates the anti-noise signal from the lowered resolution second reference microphone signal digital representation to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit implements a coefficient control block that shapes the response of the adaptive filter in conformity with the reference microphone signal by adapting the response of the adaptive filter. - View Dependent Claims (23)
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24. 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; converting the reference microphone signal to generate a first reference microphone digital representation at a firsst sample rate using an analog-to-digital converter; quantizing the first reference microphone signal digital representation at the first sample rate to generate a lowered resolution second reference microphone signal digital representation at the first sample rate using a sigma-delta shaper; and adaptively generating an anti-noise signal from the lowered resolution second reference microphone signal digital representation for countering the effects of ambient audio sounds at an acoustic output of the transducer by adapting a response of an adaptive filter that filters the lowered resolution second reference microphone signal digital representation. - View Dependent Claims (25)
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26. 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; a first analog-to-digital converter for converting the reference microphone signal to a first reference microphone signal digital representation at a first sample rate; a first sigma-delta quantizer that quantizes the first digital representation at the first sample rate to generate a lowered resolution second reference microphone signal digital representation at the first sample rate; and a processing circuit that implements an adaptive filter having a response that generates the anti-noise signal from the lowered resolution second reference microphone signal digital representation to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit implements a coefficient control block that shapes the response of the adaptive filter in conformity with the reference microphone signal by adapting the response of the adaptive filter. - View Dependent Claims (27)
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Specification