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; 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 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.
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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 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
42 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 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. - View Dependent Claims (2, 3, 4)
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5. 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 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; and 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. - View Dependent Claims (6, 7, 8)
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9. 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; 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 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. - View Dependent Claims (10, 11, 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; 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 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 the processing circuit detects that the source audio is present, and in response to detecting that the source audio is present, alters adaptation of the adaptive filter. - View Dependent Claims (14)
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15. 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; 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 adapting a response of an adaptive filter that filters an output of the reference microphone; detecting whether or not the source audio is present; and
.responsive to detecting that the source audio is present, altering adaptation of the adaptive filter. - View Dependent Claims (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; 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 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 the processing circuit detects that the source audio is present, and in response to detecting that the source audio is present, alters adaptation of the adaptive filter. - View Dependent Claims (18)
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19. 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 concerting 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 at least one filter having a high-pass characteristic and coupled between at least one of the first analog-to-digital converter or the second analog-to-digital converter and the coefficient control block for removing first DC components from a first input to the coefficient control block. - View Dependent Claims (20, 21)
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22. 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; filtering at least one of the first digital representation or the second representation; and adaptively generating an anti-noise signal from the first digital representation and the second 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 an output of the reference microphone, wherein the filtering acts to remove first DC components from a first input to a coefficient control block that controls the adaptive filter. - View Dependent Claims (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; a first analog-to-digital converter for concerting 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 at least one filter having a high-pass characteristic and coupled between at least one of the first analog-to-digital converter or the second analog-to-digital converter and the coefficient control block for removing first DC components from a first input to the coefficient control block. - View Dependent Claims (26, 27)
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28. 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 concerting 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 filter having a high-pass characteristic coupled between the first analog-to-digital converter and an input to the adaptive filter for removing first DC components from the input to the adaptive filter. - View Dependent Claims (29, 30)
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31. 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; and adaptively generating an anti-noise signal from the first digital representation and the second 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 an output of the reference microphone, wherein the filtering acts to remove first DC components from an input to the adaptive filter. - View Dependent Claims (32, 33)
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34. 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 filter having a high-pass characteristic coupled between the first analog-to-digital converter and an input to the adaptive filter for removing first DC components from the input to the adaptive filter. - View Dependent Claims (35, 36)
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37. 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 sigma-delta quantizer that quantizes the reference microphone signal to generate a lowered resolution microphone signal; and a processing circuit that implements an adaptive filter having a response that generates the anti-noise signal from the lowered resolution 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 reference microphone signal by adapting the response of the adaptive filter. - View Dependent Claims (38)
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39. 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; quantizing the reference microphone signal to generate a lowered resolution microphone signal using a sigma-delta modulator; and adaptively generating an anti-noise signal from the result of the quantizing 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 an output of the reference microphone. - View Dependent Claims (40)
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41. 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 implements an adaptive filter having a response that generates the anti-noise signal from the lowered resolution 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. - View Dependent Claims (42)
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Specification