DETECTION AND SUPPRESSION OF WIND NOISE IN MICROPHONE SIGNALS

• US 20080226098A1
• Filed: 10/26/2007
• Published: 09/18/2008
• Est. Priority Date: 04/29/2005
• Status: Active Grant

• Current Assignee: Cerence Inc., Cerence Operating Company (Cerence Inc.)
• Original Assignee: Nuance Communications, Inc. (Microsoft Corporation)
• Inventors: Haulick, Tim, Hetherington, Phillip A., Buck, Markus, Haindl, Klaus
• Granted Patent: US 8,194,881 B2
• Time in Patent Office: Days
• US Class Current: 381/94.9
• CPC Class Codes: G10L 2021/02166 Microphone arrays; Beamforming
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 2410/01 Noise reduction using microphones having different directional characteristics
• CPC Class Codes: H04R 2410/07 Mechanical or electrical reduction of wind noise generated by wind passing a microphone
• CPC Class Codes: H04R 2499/13 Acoustic transducers and sound field adaptation in vehicles
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

To reliably and consistently detect desirable sounds, a system detects the presence of wind noise based on the power levels of audio signals. A first transducer detects sound originating from a first direction and a second transducer detects sound originating from a second direction. The power levels of the sound are compared. When the power level of the sound received from the second transducer is less than the power level of the sound received from the first transducer by a predetermined value, wind noise may be present. A signal processor may generate an output from one or a combination of the audio signals, based on a wind noise detection.

Claims

1. A system, comprising:

a first transducer with a first directivity index and configured to detect a first audio signal, where the first directivity index is non-zero and the first audio signal has a first power level;

a second transducer with a second directivity index and configured to detect a second audio signal, where the second directivity index is less than the first directivity index and the second audio signal has a second power level;

a detector configured to output a detection signal based on a comparison of the first power level and the second power level, the detection signal indicating presence of wind noise if the second power level is less than the first power level by a predetermined value, and indicating absence of wind noise if the second power level is not less than the first power level by the predetermined value; and

a signal processor configured to output an output signal from the first audio signal, the second audio signal, or combinations thereof, based on the detection signal.

2. The system of claim 1, where the output signal is generated from the first audio signal if the detection signal indicates the absence of wind noise.

3. The system of claim 1, where the output signal is generated from the second audio signal if the detection signal indicates the presence of wind noise.

4. The system of claim 1, where the output signal is generated from a combination of the first audio signal and the second audio signal if the detection signal indicates the presence of wind noise or the detection signal is not output, the combination comprising a portion of the first audio signal above a predetermined frequency and a portion of the second audio signal below the predetermined frequency.

5. The system of claim 1, where the signal processor comprises a threshold frequency calculator configured to calculate a threshold frequency based on the first power level and the second power level, the threshold frequency calculated such that the second power level is not less than the first power level by the predetermined value in frequencies above the threshold frequency.

6. The system of claim 5, where the output signal is generated from a combination of the first audio signal for frequencies above the threshold frequency and the second audio signal for frequencies below the threshold frequency, if the detection signal indicates the presence of wind noise, the combination comprising phase values of the second audio signal and amplitude values of the first audio signal and the second audio signal.

7. The system of claim 6, where the amplitude values comprise a minimum of a spectral value of the first audio signal and a spectral value of the second audio signal, for each frequency below the threshold frequency.

8. The system of claim 1, further comprising a beamformer configured to output the first audio signal with the first power level based on a combination of audio signals from each of a plurality of transducers, the plurality of transducers each having a directivity index greater than the second directivity index.

9. The system of claim 1, further comprising a delay module configured to keep the detection signal constant for a first predetermined time period and the threshold frequency constant for a second predetermined time period.

10. The system of claim 1, where the detector comprises a comparator for comparing the first power level and the second power level, and a selector for allowing selection of the predetermined value.

11. The system of claim 1, where the system is in communication with a vehicle.

12. A method, comprising:

detecting a first audio signal with a first power level, the first audio signal originating from a specific direction;

detecting a second audio signal with a second power level, the second audio signal originating from any direction;

comparing the first and second power levels;

outputting a detection signal indicating presence of wind noise when the second power level is less than the first power level by a predetermined value, or absence of wind noise when the second power level is not less than the first power level by the predetermined value; and

generating an output signal from the first audio signal, the second audio signal, or combinations thereof, based on the detection signal.

13. The method of claim 12, where the output signal is generated from the first audio signal when the detection signal indicates the absence of wind noise.

14. The method of claim 12, where the output signal is generated from the second audio signal when the detection signal indicates the presence of wind noise.

15. The method of claim 12, where the output signal is generated from a combination of the first audio signal and the second audio signal when the detection signal indicates the presence of wind noise or the detection signal is not output, the combination comprising a portion of the first audio signal above a predetermined frequency and a portion of the second audio signal below the predetermined frequency.

16. The method of claim 12, further comprising calculating a threshold frequency based on the first power level and the second power level, the threshold frequency calculated such that the second power level is not less than the first power level by the predetermined value in frequencies above the threshold frequency.

17. The method of claim 16, where the output signal is generated from a combination of the first audio signal and the second audio signal for frequencies below the threshold frequency if the detection signal indicates the presence of wind noise, the combination comprising phase values of the second audio signal and amplitude values of the first audio signal and the second audio signal.

18. The method of claim 17, where the amplitude values comprise a minimum of a spectral value of the first audio signal and a spectral value of the second audio signal, for each frequency below the threshold frequency.

19. The method of claim 12, further comprising beamforming a plurality of audio signals originating from a plurality of specific directions to generate the first audio signal with the first power level.

20. The method of claim 12, further comprising keeping the detection signal constant for a first predetermined time period and keeping the threshold frequency substantially constant for a second predetermined time period.

21. A system, comprising:

a first transducer configured to detect a first audio signal originating from a specific direction, where the first audio signal has a first power level;

a second transducer configured to detect a second audio signal originating from a second direction, where the second audio signal has a second power level;

a comparator configured to output a detection signal based on a comparison of the first power level and the second power level, the detection signal indicating presence of wind noise if the second power level is less than the first power level by a predetermined value, and indicating absence of wind noise if the second power level is not less than the first power level by the predetermined value; and

an output signal generator configured to generate an output signal from the first audio signal, if the detection signal indicates the absence of wind noise, and from the second audio signal, if the detection signal indicates the presence of wind noise.

22. The system of claim 21, where the output signal generator is further configured to generate the output signal from a combination of the first and second audio signals, when the detection signal indicates the presence of wind noise, or if the comparator does not output the detection signal.

23. The system of claim 22, where the combination comprises a portion of the first audio signal above a predetermined frequency and a portion of the second audio signal below the predetermined frequency.

24. The system of claim 21, further comprising a threshold frequency calculator configured to calculate a threshold frequency, and where the output signal generator is further configured to generate the output signal from a combination of the first and second audio signals, the combination comprising a portion of the first audio signal above the threshold frequency and a portion of the second audio signal below the threshold frequency.

25. The system of claim 21, further comprising a beamformer configured to output the first audio signal with the first power level, the first audio signal comprising audio signals originating from specific directions, each of the audio signals provided by each of a plurality of transducers.