Method and apparatus for masking wind noise

Patent metadata

Field	Value
Publication number	US-8983833-B2
Application number	US-201113012062-A
Country	US
Kind code	B2
Filing date	Jan 24, 2011
Priority date	Jan 24, 2011
Publication date	Mar 17, 2015
Grant date	Mar 17, 2015

Abstract

Wind and other noise is suppressed in a signal by adaptively changing characteristics of a filter. The filter characteristics are changed in response to the noise content of the signal over time using a history of noise content. Filter characteristics are changed according to a plurality of reference filters, the characteristics of which are chosen to optimally attenuate or amplify signals in a range of frequencies.

First claim

What is claimed is:

1. A method of suppressing wind noise in an audio signal obtained from a microphone, the method comprising:
receiving audio frequency signals at a low pass filter, the audio frequency signals being received by the low pass filter from a microphone, said audio frequency signals comprising at least one of: noise, speech and a combination of noise and speech;
generating a wind noise probability by calculating a smoothened power ratio based on a ratio of signals output from the low pass filter to the audio frequency signals received from the microphone, wherein the smoothened power ratio represents a wind noise probability;
selecting a reference filter from a plurality of reference filters based on the wind noise probability;
selecting a cogent frequency of an adaptive filter coupled to the microphone and changing an attenuation of the adaptive filter at the selected cogent frequency, the adaptive filter cogent frequency being selected from a plurality of frequencies using at least one characteristic of the selected reference filter, the selecting of a cogent frequency of the adaptive filter and the changing of the attenuation of the adaptive filter being made responsive to evaluation of the wind noise probability, thereby changing a pass band characteristic of the adaptive filter;
generating and outputting different filter coefficients from the adaptive filter responsive to different wind noise probabilities; and
multiplying digital representations of audio frequency signals from the microphone by filter coefficients of the adaptive filter to produce a noise-reduced output signal;
wherein the steps of: generating a wind noise probability, selecting a reference filter, selecting a cogent frequency of an adaptive filter, changing an attenuation of an adaptive filter, generating and outputting filter coefficients and multiplying digital representations of audio frequency signals from the microphone by coefficients of the adaptive filter, are performed continuously to continuously change a shape of the adaptive filter's pass band responsive to changing characteristics of wind noise in the audio frequency signals.

2. The method of claim 1 , wherein the step of multiplying digital representations of audio frequency signals from the microphone by coefficients of the adaptive filter to produce a noise-reduced output signal, is not performed when noise is not present in the audio frequency signals received by the filter from the microphone.

3. The method of claim 1 , wherein the step of generating a wind noise probability is further comprised of:
filtering the input signal to provide a filtered portion of the signal; and
comparing a relationship between the input signal and the filtered portion of the signal to a plurality of threshold values.

4. The method of claim 1 , wherein the wind noise probability is identified based on comparison with thresholds.

5. The method of claim 4 , wherein the value of each threshold of the plurality of thresholds is predetermined.

6. The method of claim 1 , wherein each filter of the plurality of reference filters optionally has one or more corresponding cogent frequencies and one or more corresponding attenuations.

7. The method of claim 1 , further comprising the step of smoothening the one or more corresponding gains of each reference filter.

8. The method of claim 7 , further comprising the step of using different values for a smoothing coefficient to calculate a smoothened gain of each filter of the plurality of filters based on at least one type of a wind noise-probability transition selected from:
a speech-to-noise transition; and
a noise-to-speech transition.

9. The method of claim 6 , further comprising the step of smoothening a frequency response of each reference filter.

10. The method of claim 6 , further comprising the step of using different smoothing coefficients to calculate a smoothened cogent frequency of each filter of the plurality of filters based on at least one type of a wind noise-probability transition selected from:
a speech-to-noise transition; and
a noise-to-speech transition.

11. The method of claim 10 , further comprising the step of selecting a plurality of cogent frequencies for a corresponding number of reference filters.

12. The method of claim 1 , further comprising the step of modifying a frequency response of the reference filters based on a selected attenuation.

13. The method of claim 1 , further comprising the step of modifying a frequency response of the reference filters based on one or more attenuations and one or more cogent frequencies.

14. The method of claim 1 , further comprising the step of: separately modifying a frequency response above and below a cogent frequency based on a selected gain.

15. An apparatus comprising:
a microphone;
an analog-to-digital converter receiving audio signals from the microphone and providing digital signals representing said audio signals;
a processor configured to receive digital signals representing audio signals obtained from the microphone; and
a memory device coupled to the processor, the memory device storing program instructions, which when executed by the processor cause the processor to:
generate a wind noise probability by calculating a smoothened power ratio using the digital signals representing the audio signals obtained from the microphone and a low pass filtered version of the digital signal;
adaptively filter microphone signals by:
selecting a reference filter based at least in part on the wind noise probability; and
selecting a cogent filter frequency and changing an attenuation at the selected cogent filter frequency responsive to changing wind noise levels in the audio frequency signals from the microphone and responsive to characteristics of the selected reference filter, thereby changing a pass band filter characteristic responsive to wind noise in the audio frequency signals from the microphone;
generate filter coefficients responsive to different wind noise probabilities; and
multiply digital representations of audio frequency signals from the microphone by filter coefficients to produce a wind-noise-reduced output signal;
wherein, the selecting a reference filter, selecting a cogent frequency, changing an attenuation at the selected cogent frequency, generating filter coefficients and multiplying digital representations of audio frequency signals by filter coefficients, are performed continuously to continuously change a pass band filter characteristic responsive to wind noise in the audio frequency signals from the microphone.

16. The apparatus of claim 15 , wherein the memory device stores program instructions, which when executed by the processor cause the processor to: provide a reference filter based on the wind noise probability, wherein the selected reference filter is configured to selectively attenuate signals in a range of frequencies of the wind noise, attenuated signals comprising wind noise signals.

17. The apparatus of claim 15 , further comprising a memory device having program instructions, which when executed by the processor cause the processor to omit the step of, multiplying digital representations of audio frequency signals from the microphone by coefficients of the adaptive filter to produce a noise-reduced output signal, when wind noise is not present in the audio frequency signals received by the filter.

18. The apparatus of claim 15 , further comprising a memory device having program instructions, which when executed, cause the processor to generate a wind noise p

Assignees

• Joshi Bijal
• Yeldener Suat
• Continental Automotive Systems

Inventors

• Joshi Bijal
• Yeldener Suat

Classifications

• G10L21/0208

  Noise filtering · CPC title

• G10L21/0232

  Processing in the frequency domain · CPC title

• H04R2410/07

  Mechanical or electrical reduction of wind noise generated by wind passing a microphone · CPC title

• G10L2021/02163

  Only one microphone · CPC title

• H04R3/00 Primary

  Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) · CPC title