System and method for providing noise suppression utilizing null processing noise subtraction

• US 20090323982A1
• Filed: 06/30/2008
• Published: 12/31/2009
• Est. Priority Date: 01/30/2006
• Status: Active Grant

• Current Assignee: Knowles Electronics Llc (Knowles Corporation)
• Original Assignee: Knowles Electronics Llc (Knowles Corporation)
• Inventors: Murgia, Carlo, Solbach, Ludger
• Granted Patent: US 9,185,487 B2
• Time in Patent Office: Days
• US Class Current: 381/94.3
• CPC Class Codes: G10L 2021/02166 Microphone arrays; Beamforming
• CPC Class Codes: G10L 21/0232 Processing in the frequency domain
• CPC Class Codes: G10L 21/0308 characterised by the type of parameter measurement, e.g. correlation techniques, zero crossing techniques or predictive techniques
• CPC Class Codes: H04R 2410/01 Noise reduction using microphones having different directional characteristics
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

Systems and methods for noise suppression using noise subtraction processing are provided. The noise subtraction processing comprises receiving at least a primary and a secondary acoustic signal. A desired signal component may be calculated and subtracted from the secondary acoustic signal to obtaining a noise component signal. A determination may be made of a reference energy ratio and a prediction energy ratio. A determination may be made as to whether to adjust the noise component signal based partially on the reference energy ratio and partially on the prediction energy ratio. The noise component signal may be adjusted or frozen based on the determination. The noise component signal may then be removed from the primary acoustic signal to generate a noise subtracted signal which may be outputted.

Claims

1. A method for suppressing noise, comprising:

receiving at least a primary and a secondary acoustic signal;

subtracting a desired signal component from the secondary acoustic signal to obtain a noise component signal;

performing a first determination of at least one energy ratio related to the desired signal component and the noise component signal;

performing a second determination of whether to adjust the noise component signal based on the at least one energy ratio;

adjusting the noise component signal based on the second determination;

subtracting the noise component signal from the primary acoustic signal to generate a noise subtracted signal; and

outputting the noise subtracted signal.

2. The method of claim 1 wherein subtracting the desired signal component comprises applying a coefficient representing a source location to the primary acoustic signal to generate the desired signal component.

3. The method of claim 1 wherein the at least one energy ratio comprises a reference energy ratio and a prediction energy ratio.

4. The method of claim 3 further comprising adapting an adaptation coefficient applied to the noise component signal when the prediction energy ratio is greater than the reference energy ratio.

5. The method of claim 3 further comprising freezing an adaptation coefficient applied to the noise component signal when the prediction energy ratio is less than the reference energy ratio.

6. The method of claim 1 further comprising determining a NP gain based on the at least one energy ratio indicating how much of the primary acoustic signal has been cancelled out of the noise subtracted signal.

7. The method of claim 6 further comprising providing the NP gain to a multiplicative noise suppression system.

8. The method of claim 1 wherein the primary and secondary acoustic signals are separated into sub-band signals.

9. The method of claim 1 wherein outputting the noise subtracted signal comprises outputting the noise subtracted signal to a multiplicative noise suppression system.

10. The method of claim 9 wherein the multiplicative noise suppression system comprises generating a gain mask based at least on the noise subtracted signal.

11. The method of claim 10 further comprising applying the gain mask to the noise subtracted signal to generate an audio output signal.

12. A system for suppressing noise, comprising:

a microphone array configured to receive at least a primary and a secondary acoustic signal;

an analysis module configured to generate a desired signal component which may be subtracted from the secondary acoustic signal to obtain a noise component signal;

a gain module configured to perform a first determination of at least one energy ratio related to the desired signal component and the noise component signal;

an adaptation module configured to perform a second determination of whether to adjust the noise component signal based on the at least one energy ratio, the adaption module further configured to adjust the noise component signal based on the second determination; and

at least one summing module configured to subtract the desired signal component from the secondary acoustic signal and to subtract the noise component signal from the primary acoustic signal to generate a noise subtracted signal.

13. The system of claim 12 wherein the analysis module is configured to apply a coefficient representing a source location to the primary acoustic signal to generate the desired signal component.

14. The system of claim 12 wherein the at least one energy ratio comprises a reference energy ratio and a prediction energy ratio.

15. The system of claim 14 wherein the adaptation module is configured to adapt an adaptation coefficient applied to the noise component signal when the prediction energy ratio is greater than the reference energy ratio.

16. The system of claim 14 wherein the adaptation module is configured to freeze an adaptation coefficient applied to the noise component signal when the prediction energy ratio is less than the reference energy ratio.

17. The system of claim 12 wherein further comprising a gain module configured to determine a NP gain based on the at least one energy ratio indicating how much of the primary acoustic signal has been cancelled out of the noise subtracted signal.

18. A machine readable medium having embodied thereon a program, the program providing instructions for a method for suppressing noise using noise subtraction processing, the method comprising:

receiving at least a primary and a secondary acoustic signal;

subtracting a desired signal component from the secondary acoustic signal to obtain a noise component signal;

performing a first determination of at least one energy ratio related to the desired signal component and the noise component signal;

performing a second determination of whether to adjust the noise component signal based on the at least one energy ratio;

adjusting the noise component signal based on the second determination;

subtracting the noise component signal from the primary acoustic signal to generate a noise subtracted signal; and

outputting the noise subtracted signal.

19. The machine readable medium of claim 18 wherein the at least one energy ratio comprises a reference energy ratio and a prediction energy ratio.

20. The machine readable medium of claim 19 wherein the method further comprises adapting an adaptation coefficient applied to the noise component signal when the prediction energy ratio is greater than the reference energy ratio.

21. The machine readable medium of claim 19 wherein the method further comprises freezing an adaptation coefficient applied to the noise component signal when the prediction energy ratio is less than the reference energy ratio.