System and method for multi-channel noise suppression based on closed-form solutions and estimation of time-varying complex statistics

• US 8,965,757 B2
• Filed: 11/14/2011
• Issued: 02/24/2015
• Est. Priority Date: 11/12/2010
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Thyssen, Jes, Zeng, Huaiyu, Chen, Juin-Hwey, Sollenberger, Nelson, Zhang, Xianxian
• Primary Examiner(s): Chawan, Vijay B
• Application Number:
  US13/295,818
• Publication Number:
  US 20120123772A1
• Time in Patent Office: 1,198 Days
• Field of Search: 704226-228, 704/233, 704/225, 704/203, 704/207, 381/94.3, 381/94.1, 381/94.2, 381/94.7, 381/71.11, 381/317, 381/321, 381/320, 379/406.08, 379/395
• US Class Current: 704/226
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 21/0272 Voice signal separating
• CPC Class Codes: H04R 1/245 of microphones
• CPC Class Codes: H04R 2410/07 Mechanical or electrical reduction of wind noise generated by wind passing a microphone

Abstract

Multi-channel noise suppression systems and methods are described that omit the traditional delay-and-sum fixed beamformer in devices that include a primary speech microphone and at least one noise reference microphone with the desired speech being in the near-field of the device. The multi-channel noise suppression systems and methods use a blocking matrix (BM) to remove desired speech in the input speech signal received by the noise reference microphone to get a “cleaner” background noise component. Then, an adaptive noise canceler (ANC) is used to remove the background noise in the input speech signal received by the primary speech microphone based on the “cleaner” background noise component to achieve noise suppression. The filters implemented by the BM and ANC are derived using closed-form solutions that require calculation of time-varying statistics of complex frequency domain signals in the noise suppression system.

Claims

1. A system for suppressing noise in a primary input speech signal that comprises a first desired speech component and a first background noise component using a reference input speech signal that comprises a second desired speech component and a second background noise component, the system comprising:

a blocking matrix configured to filter the primary input speech signal, in accordance with a first transfer function, to estimate the second desired speech component and to remove the estimate of the second desired speech component from the reference input speech signal to provide an adjusted second background noise component;

an adaptive noise canceler configured to filter the adjusted second background noise component, in accordance with a second transfer function, to estimate the first background noise component and to remove the estimate of the first background noise component from the primary input speech signal to provide a noise suppressed primary input speech signal,

wherein the first transfer function is determined based on statistics of the first desired speech component and the second desired speech component, and the second transfer function is determined based on statistics of the primary input speech signal and the adjusted second background noise component.

2. The system of claim 1, wherein the statistics of the first desired speech component and the second desired speech component comprise:

desired speech statistics of the primary input speech signal determined based on an estimate of a power spectrum of the first desired speech component, and

desired speech cross-channel statistics determined based on an estimate of a cross-spectrum between the first desired speech component and the second desired speech component.

3. The system of claim 2, wherein the blocking matrix comprises a statistics estimator configured to:

estimate the power spectrum of the first desired speech component based on a product of a spectrum of the primary input speech signal and a complex conjugate of the spectrum of the primary input speech signal, and

update the desired speech statistics of the primary input speech signal with the product of the spectrum of the primary input speech signal and the complex conjugate of the spectrum of the primary input speech signal at a rate related to a difference in energy or level between the primary input speech signal and the reference input speech signal.

4. The system of claim 2, wherein the blocking matrix comprises a statistics estimator configured to:

estimate the cross-spectrum between the first desired speech component and the second desired speech component based on a spectrum of the reference input speech signal and the spectrum of the primary input speech signal, and

update the desired speech cross-channel statistics based on the spectrum of the reference input speech signal and the spectrum of the primary input speech signal at a rate related to a difference in energy or level between the primary input speech signal and the reference input speech signal.

5. The system of claim 1, wherein the first transfer function is further determined based on statistics of the first background noise component and the second background noise component.

6. The system of claim 5, wherein the statistics of the first background noise component and the second background noise component comprise:

stationary background noise statistics of the primary input speech signal determined based on a spectrum of the primary input speech signal, and

stationary background noise cross-channel statistics determined based on a spectrum of the primary input speech signal and a spectrum of the reference input speech signal.

7. The system of claim 6, wherein the blocking matrix comprises a statistics estimator configured to:

update the stationary background noise statistics of the primary input speech signal with the product of the spectrum of the primary input speech signal and the complex conjugate of the spectrum of the primary input speech signal at a rate related to a difference in energy or level between the primary input speech signal and the reference input speech signal.

8. The system of claim 6, wherein the blocking matrix comprises a statistics estimator configured to:

update the stationary background noise cross-channel statistics based on the spectrum of the primary input speech signal and the spectrum of the reference input speech signal at a rate related to a difference in energy or level between the primary input speech signal and the reference input speech signal.

9. The system of claim 1, wherein the statistics of the primary input speech signal and the adjusted second background noise component comprise:

background noise statistics determined based on a product of a spectrum of the adjusted second background noise component and a complex conjugate of the spectrum of the adjusted second background noise component, and

cross-channel background noise statistics determined based on a spectrum of the primary input speech signal and the spectrum of the adjusted second background noise component.

10. The system of claim 9, wherein the adaptive noise canceler comprises a statistics estimator configured to:

update the background noise statistics with the product of the spectrum of the adjusted second background noise component and the complex conjugate of the spectrum of the adjusted second background noise component at a rate related to a difference in energy or level between the primary input speech signal and the adjusted second background noise component.

11. The system of claim 9, wherein the adaptive noise canceler comprises a statistics estimator configured to:

update the cross-channel background noise statistics based on the spectrum of the primary input speech signal and the spectrum of the adjusted second background noise component at a rate related to a difference in energy or level between the primary input speech signal and the adjusted second background noise component.

12. The system of claim 9, wherein the adaptive noise canceler comprises a statistics estimator configured to:

update a fast version of the background noise statistics with the product of the spectrum of the adjusted second background noise component and the complex conjugate of the spectrum of the adjusted second background noise component at a first rate related to a difference in energy or level between the primary input speech signal and the adjusted second background noise component,

update a slow version of the background noise statistics with the product of the spectrum of the adjusted second background noise component and the complex conjugate of the spectrum of the adjusted second background noise component at a second rate different from the first rate and related to a difference in energy or level between the primary input speech signal and the adjusted second background noise component, and

select between the fast version of the background noise statistics and the slow version of the background noise statistics to determine the second transfer function based on which background noise statistics result in the noise suppressed primary input speech signal having a smaller energy.

13. The system of claim 9, wherein the adaptive noise canceler comprises a statistics estimator configured to:

update a fast version of the cross-channel background noise statistics based on the spectrum of the primary input speech signal and the spectrum of the adjusted second background noise component at a first rate related to a difference in energy or level between the primary input speech signal and the adjusted second background noise component,

update a slow version of the cross-channel background noise statistics based on the spectrum of the primary input speech component and the spectrum of the adjusted second background noise component at a second rate different from the first rate and related to a difference in energy or level between the primary input speech signal and the adjusted second background noise component, and

select between the fast version of the cross-channel background noise statistics and the slow version of the cross-channel background noise statistics to determine the second transfer function based on which cross-channel background noise statistics result in the noise suppressed primary input speech signal having a smaller energy.

14. The system of claim 1, wherein the blocking matrix receives and processes the primary input speech signal in the frequency domain.

15. The system of claim 1, wherein the blocking matrix receives and processes the primary input speech signal in the frequency domain using a plurality of time direction filters, each of the plurality of time direction filters configured to filter a different sub-band or frequency component of the primary input speech signal.

16. The system of claim 1, wherein the adaptive noise canceler receives and processes the adjusted second background noise component in the frequency domain.

17. The system of claim 1, wherein the adaptive noise canceler receives and processes the adjusted second background noise signal in the frequency domain using a plurality of time direction filters, each of the plurality of time direction filters configured to filter a different sub-band or frequency component of the adjusted second background noise component.

18. The system of claim 1, further comprising:

a microphone mismatch estimator configured to estimate a difference in microphone sensitivity between a first microphone that receives the primary input speech signal and a second microphone that receives the reference input speech signal.

19. The system of claim 18, wherein the microphone mismatch estimator is further configured to identify a presence of a diffuse sound field at least in part based on the primary input speech signal and the reference input speech signal and update the estimated difference in microphone sensitivity when the presence of the diffuse sound field is identified.

20. A method for suppressing noise in a primary signal that comprises a first desired speech signal and a first noise signal using a reference signal that comprises a second desired speech signal and a second noise signal, the method comprising:

filtering the primary input speech signal in accordance with a first transfer function to estimate the second desired speech signal;

removing the estimate of the second desired speech signal from the reference signal to provide an adjusted second noise signal;

filtering the adjusted second noise signal, in accordance with a second transfer function, to estimate the first noise signal;

removing the estimate of the first noise signal from the primary signal to provide a noise suppressed primary signal;

determining the first transfer function based on statistics of the first desired speech signal and the second desired speech signal; and

determining the second transfer function based on statistics of the primary signal and the adjusted second noise signal.