SYSTEMS AND METHODS FOR DETECTION AND CANCELLATION OF NARROW-BAND NOISE

• US 20140369517A1
• Filed: 06/14/2013
• Published: 12/18/2014
• Est. Priority Date: 06/14/2013
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Zhou, Dayong, Lu, Yang
• Granted Patent: US 9,264,808 B2
• Time in Patent Office: Days
• US Class Current: 381/71.11
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17835 using detection of abnormal input signals
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/108 Communication systems, e.g. where useful sound is kept and noise is cancelled
• CPC Class Codes: G10K 2210/503 Diagnostics; Stability; Alarms; Failsafe
• CPC Class Codes: H04R 2460/01 Hearing devices using active noise cancellation
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

In accordance with methods and systems of the present disclosure, an integrated circuit for implementing at least a portion of a personal audio device may include an output including an anti-noise signal, a reference microphone input, an error microphone input, and a processing circuit. The processing circuit may implement 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 may implement 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 in accordance with a calculated narrow-band-to-full-band ratio, wherein the narrow-band-to-full-band ratio is a function of a narrow-band power of the reference microphone signal divided by a full-band power of the reference microphone signal.

Claims

1. A personal audio device comprising:

a personal audio device housing;

a transducer coupled to 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 coupled to the housing for providing a reference microphone signal indicative of the ambient audio sounds;

an error microphone coupled to 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 in the error microphone signal and by further adapting the response of the adaptive filter in accordance with a calculated narrow-band-to-full-band ratio, wherein the narrow-band-to-full-band ratio is a function of a narrow-band power of the reference microphone signal divided by a full-band power of the reference microphone signal.

2. The personal audio device of claim 1, wherein the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a present full-band power of the reference microphone signal.

3. The personal audio device of claim 1, wherein the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a quantity equal to a present full-band power of the reference microphone signal minus a present power of reference microphone signal outliers present outside of a frequency range of the narrow-band power.

4. The personal audio device of claim 1, wherein:

the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a present full-band power of the reference microphone signal responsive to a determination that no disturbance is detected on the reference microphone signal; and

the narrow-band-to-full-band ratio is calculated as equal to the previous value of the narrow-band-to-full-band ratio reference microphone signal responsive to a determination that a disturbance is detected on the reference microphone signal.

5. The personal audio device of claim 1, wherein the narrow-band power comprises a power of the reference microphone signal for frequencies between approximately 50 Hz and approximately 380 Hz.

6. The personal audio device of claim 1, wherein the processing circuitry adapts the response of the adaptive filter in accordance with the calculated narrow-band-to-full-band ratio by controlling a step size of at least one coefficient of the coefficient control block based on the calculated narrow-band-to-full-band ratio.

7. The personal audio device of claim 1, wherein the processing circuitry adapts the response of the adaptive filter in accordance with the calculated narrow-band-to-full-band ratio by controlling an adaptive noise control gain of the adaptive filter based on the calculated narrow-band-to-full-band ratio.

8. The personal audio device of claim 1, wherein the narrow-band power of the reference microphone signal is attributable primarily to ambient noise caused by travel in a vehicle.

9. A method for canceling ambient audio sounds in the proximity of a transducer of a personal audio device, the method comprising:

receiving a reference microphone signal indicative of the ambient audio sounds;

receiving an error microphone signal indicative of the output of the transducer and the ambient audio sounds at the transducer;

adaptively generating an anti-noise signal, from a result of the measuring with the reference microphone and the measuring with the error microphone, 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 to minimize the ambient audio sounds in the error microphone signal, and further filters the output of the reference microphone in accordance with a calculated narrow-band-to-full-band ratio, wherein the narrow-band-to-full-band ratio is a function of a narrow-band power of the reference microphone signal divided by a full-band power of the reference microphone signal; and

combining the anti-noise signal with a source audio signal to generate an audio signal provided to the transducer.

10. The method of claim 9, wherein the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a present full-band power of the reference microphone signal.

11. The method of claim 9, wherein the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a quantity equal to a present full-band power of the reference microphone signal minus a present power of reference microphone signal outliers present outside of a frequency range of the narrow-band power.

12. The method of claim 9, wherein:

the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a present full-band power of the reference microphone signal responsive to a determination that no disturbance is detected on the reference microphone signal; and

the narrow-band-to-full-band ratio is calculated as equal to the previous value of the narrow-band-to-full-band ratio reference microphone signal responsive to a determination that a disturbance is detected on the reference microphone signal.

13. The method of claim 9, wherein the narrow-band power comprises a power of the reference microphone signal for frequencies between approximately 50 Hz and approximately 380 Hz.

14. The method of claim 9, wherein adapting the response of the adaptive filter in accordance with the calculated narrow-band-to-full-band ratio comprises controlling a step size of at least one coefficient of the coefficient control block based on the calculated narrow-band-to-full-band ratio.

15. The method of claim 9, wherein adapting the response of the adaptive filter in accordance with the calculated narrow-band-to-full-band ratio comprises controlling an adaptive noise control gain of the adaptive filter based on the calculated narrow-band-to-full-band ratio.

16. The method of claim 9, wherein the narrow-band power of the reference microphone signal is attributable primarily to ambient noise caused by travel in a vehicle.

17. 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 effect 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 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 in the error microphone signal and further adapting the response of the adaptive filter in accordance with a calculated narrow-band-to-full-band ratio, wherein the narrow-band-to-full-band ratio is a function of a narrow-band power of the reference microphone signal divided by a full-band power of the reference microphone signal.

18. The integrated circuit of claim 17, wherein the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a present full-band power of the reference microphone signal.

19. The integrated circuit of claim 17, wherein the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a quantity equal to a present full-band power of the reference microphone signal minus a present power of reference microphone signal outliers present outside of a frequency range of the narrow-band power.

20. The integrated circuit of claim 17, wherein:

the narrow-band-to-full-band ratio is calculated as a blended average of a previous value of the narrow-band-to-full-band ratio and a quantity equal to a present narrow-band power of the reference microphone signal divided by a present full-band power of the reference microphone signal responsive to a determination that no disturbance is detected on the reference microphone signal; and

the narrow-band-to-full-band ratio is calculated as equal to the previous value of the narrow-band-to-full-band ratio reference microphone signal responsive to a determination that a disturbance is detected on the reference microphone signal.

21. The integrated circuit of claim 17, wherein the narrow-band power comprises a power of the reference microphone signal for frequencies between approximately 50 Hz and approximately 380 Hz.

22. The integrated circuit of claim 17, wherein the processing circuitry adapts the response of the adaptive filter in accordance with the calculated narrow-band-to-full-band ratio by controlling a step size of at least one coefficient of the coefficient control block based on the calculated narrow-band-to-full-band ratio.

23. The integrated circuit of claim 17, wherein the processing circuitry adapts the response of the adaptive filter in accordance with the calculated narrow-band-to-full-band ratio by controlling an adaptive noise control gain of the adaptive filter based on the calculated narrow-band-to-full-band ratio.

24. The integrated circuit of claim 17, wherein the narrow-band power of the reference microphone signal is attributable primarily to ambient noise caused by travel in a vehicle.