US 9,318,094 B2 · Adaptive noise canceling architecture for a personal audio device

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.

Claims27

Dependent claims

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.

5 more elements

An integrated circuit for implementing at least a portion of a personal audio device, comprising:

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.

4 more elements

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;
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.

5 more elements

An integrated circuit for implementing at least a portion of a personal audio device, comprising:

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.

5 more elements

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;
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.

4 more elements

An integrated circuit for implementing at least a portion of a personal audio device, comprising:

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.

3 more elements

Dependencies are inferred from the claim text.

Adaptive noise canceling architecture for a personal audio device

Life of this patent

Adaptive noise canceling architecture for a personal audio device

Life of this patent

Abstract

Claims27