Adaptive noise cancellation for multi-microphone systems

• US 8,958,572 B1
• Filed: 08/12/2010
• Issued: 02/17/2015
• Est. Priority Date: 04/19/2010
• Status: Active Grant

• Current Assignee: Knowles Electronics Llc (Knowles Corporation)
• Original Assignee: Audience Corporation
• Inventors: Solbach, Ludger
• Primary Examiner(s): ROBERTS, SHAUN A
• Application Number:
  US12/855,600
• Time in Patent Office: 1,650 Days
• Field of Search: 381/92, 381/94.1, 381/94.7, 704226-228
• US Class Current: 381/94.7
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 2410/01 Noise reduction using microphones having different directional characteristics

Abstract

Null processing noise subtraction is performed per sub-band and time frame for acoustic signals received from multiple microphones. The acoustic signals may include a primary acoustic signal and one or more additional acoustic signals. A noise component signal may be determined for each additional acoustic signal in each sub-band of signals received by N microphones by subtracting a desired signal component within every other acoustic signal weighted by a complex-valued coefficient σ from the secondary acoustic signal. The noise component signals, each weighted by a corresponding complex-valued coefficient α, may then be subtracted from the primary acoustic signal resulting in an estimate of a target signal (i.e., a noise subtracted signal).

Claims

1. A method for suppressing noise, the method comprising:

receiving a primary acoustic signal, a first secondary acoustic signal and a second secondary acoustic signal;

forming a first noise reference signal by suppressing a first speech component sub-band in the first secondary acoustic signal correlated with a speech component sub-band in the primary acoustic signal, the forming of the first noise reference signal further including suppressing a further first speech component sub-band in the first secondary acoustic signal correlated with a second speech component sub-band in the second secondary acoustic signal;

forming a second noise reference signal by suppressing the second speech component sub-band in the second secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal, the forming of the second noise reference signal further including suppressing a further second speech component sub-band in the second secondary acoustic signal correlated with the first speech component sub-band in the first secondary acoustic signal; and

reducing an energy level of a noise component sub-band in the primary acoustic signal based on the first and the second noise reference signals.

2. The method of claim 1, wherein the reducing the energy level of the noise component sub-band in the primary acoustic signal comprises suppressing the noise component sub-band in the primary acoustic signal correlated with the first and the second noise reference signals.

3. The method of claim 1, wherein the primary acoustic signal, the first secondary acoustic signal and the second secondary acoustic signal are received at respective microphones, and the primary acoustic signal is configured to be associated with any of the microphones.

4. The method of claim 1, wherein the primary acoustic signal is received from a primary microphone, the first secondary acoustic signal is received from a first secondary microphone, and the second secondary acoustic signal is received by a second secondary microphone, each of the first secondary microphone and the second secondary microphone forming a line with another microphone within a virtual cone, the virtual cone having a tip directed to a target.

5. The method of claim 4, wherein the virtual cone tip is positioned at a mouth reference point.

6. The method of claim 4, wherein the virtual cone tip is positioned at the primary microphone.

7. The method of claim 1, the method further comprising:

receiving (N−

2) additional secondary acoustic signals, wherein N is greater than two, the (N−

2) additional secondary acoustic signals not including the first secondary acoustic signal and the second secondary acoustic signal;

forming (N−

2) additional noise reference signals from the (N−

2) additional secondary acoustic signals by suppressing N speech component sub-bands in each secondary acoustic signal, the N suppressed speech component sub-bands including a suppressed speech component sub-band correlated with the speech component sub-band in the primary acoustic signal and N−

1 suppressed speech component sub-bands correlated with the other secondary acoustic signals; and

further reducing the energy level of the noise component sub-band in the primary acoustic signal based on the (N−

2) additional noise reference signals.

8. A method for suppressing noise, the method comprising:

receiving a primary acoustic signal, a first secondary acoustic signal and a second secondary acoustic signal;

forming a first noise reference signal by suppressing a first speech component sub-band in the first secondary acoustic signal correlated with a speech component sub-band in the primary acoustic signal;

forming a second noise reference signal by suppressing a second speech component sub-band in the second secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal; and

reducing an energy level of a noise component sub-band in the primary acoustic signal based on the first and the second noise reference signals;

wherein forming the first noise reference signal further includes suppressing a further first speech component sub-band in the first secondary acoustic signal correlated with the second speech component sub-band in the second secondary acoustic signal;

wherein forming the second noise reference signal further includes suppressing a further second speech component sub-band in the second secondary acoustic signal correlated with the first speech component sub-band in the first secondary acoustic signal;

wherein suppressing the first speech component sub-band in the first secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal includes applying a first coefficient to the primary acoustic signal to form a first weighted signal;

wherein suppressing the further first speech component sub-band in the first secondary acoustic signal correlated with the second speech component sub-band in the second secondary acoustic signal includes applying a second coefficient to the second secondary acoustic signal to form a second weighted signal;

wherein forming the first noise reference signal includes subtracting the first and second weighted signals from the first secondary acoustic signal;

wherein suppressing the second speech component sub-band in the second secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal includes applying a third coefficient to the primary acoustic signal to form a third weighted signal;

wherein suppressing the further second speech component sub-band in the second secondary acoustic signal correlated with the first speech component sub-band in the first secondary acoustic signal includes applying a fourth coefficient to the second secondary acoustic signal to form a fourth weighted signal; and

wherein forming the second noise reference signal includes subtracting the third and fourth weighted signals from the second secondary acoustic signal.

9. The method of claim 8, further comprising:

computing the first coefficient based on the primary acoustic signal and the first secondary acoustic signal;

computing the second coefficient based on the first and the second secondary acoustic signals;

computing the third coefficient based on the primary acoustic signal and the second secondary acoustic signal; and

computing the fourth coefficient based on the first and the second secondary acoustic signals.

10. A non-transitory computer readable storage medium having embodied thereon a program, the program being executable by a processor to perform a method for suppressing noise, the method comprising:

receiving a primary acoustic signal, a first secondary acoustic signal and a second secondary acoustic signal;

forming a first noise reference signal by suppressing a first speech component sub-band in the first secondary acoustic signal correlated with a speech component sub-band in the primary acoustic signal, the forming of the first noise reference signal further including suppressing a further first speech component sub-band in the first secondary acoustic signal correlated with a second speech component sub-band in the second secondary acoustic signal;

forming a second noise reference signal by suppressing the second speech component sub-band in the second secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal, the forming of the second noise reference signal further including suppressing a further second speech component sub-band in the second secondary acoustic signal correlated with the first speech component sub-band in the first secondary acoustic signal; and

reducing an energy level of a noise component sub-band in the primary acoustic signal based on the first and the second noise reference signals.

11. The non-transitory computer readable storage medium of claim 10, wherein the primary acoustic signal, the first secondary acoustic signal and the second secondary acoustic signal are received at respective microphones, and the primary acoustic signal is configured to be associated with any of the microphones.

12. The non-transitory computer readable storage medium of claim 10, wherein the primary acoustic signal is received from a primary microphone, the first secondary acoustic signal is received from a first secondary microphone, and the second secondary acoustic signal is received by a second secondary microphone, each of the first secondary microphone and the second secondary microphone forming a line with another microphone within a virtual cone, the virtual cone having a tip directed to a target.

13. The non-transitory computer readable storage medium of claim 12, wherein the virtual cone tip is positioned at a mouth reference point.

14. The non-transitory computer readable storage medium of claim 12, wherein the virtual cone tip is positioned at the primary microphone.

15. The non-transitory computer readable storage medium of claim 10, the method further comprising:

receiving (N−

2) additional secondary acoustic signals, wherein N is greater than two, the (N−

2) additional secondary acoustic signals not including the first secondary acoustic signal and the second secondary acoustic signal;

forming (N−

2) additional noise reference signals from the (N−

2) additional secondary acoustic signals by suppressing N speech component sub-bands in each secondary acoustic signal, the N suppressed speech component sub-bands including a suppressed speech component sub-band correlated with the speech component sub-band in the primary acoustic signal and N−

1 suppressed speech component sub-bands correlated with the other secondary acoustic signals; and

further reducing the energy level of the noise component sub-band in the primary acoustic signal based on the (N−

2) additional noise reference signals.

16. A non-transitory computer readable storage medium having embodied thereon a program, the program being executable by a processor to perform a method for suppressing noise, the method comprising:

forming a first noise reference signal by suppressing a first speech component sub-band in a first secondary acoustic signal correlated with a speech component sub-band in a primary acoustic signal;

forming a second noise reference signal by suppressing a second speech component sub-band in a second secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal; and

reducing an energy level of a noise component sub-band in the primary acoustic signal based on the first and the second noise reference signals;

wherein forming the first noise reference signal further includes suppressing a further first speech component sub-band in the first secondary acoustic signal correlated with the second speech component sub-band in the second secondary acoustic signal;

wherein forming the second noise reference signal further includes suppressing a further second speech component sub-band in the second secondary acoustic signal correlated with the first speech component sub-band in the first secondary acoustic signal;

wherein suppressing the first speech component sub-band in the first secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal includes applying a first coefficient to the primary acoustic signal to form a first weighted signal;

wherein suppressing the further first speech component sub-band in the first secondary acoustic signal correlated with the second speech component sub-band in the second secondary acoustic signal includes applying a second coefficient to the second secondary acoustic signal to form a second weighted signal;

wherein forming the first noise reference signal includes subtracting the first and second weighted signals from the first secondary acoustic signal;

wherein suppressing the second speech component sub-band in the second secondary acoustic signal correlated with the speech component sub-band in the primary acoustic signal includes applying a third coefficient to the primary acoustic signal to form a third weighted signal;

wherein suppressing the further second speech component sub-band in the second secondary acoustic signal correlated with the first speech component sub-band in the first secondary acoustic signal includes applying a fourth coefficient to the second secondary acoustic signal to form a fourth weighted signal; and

wherein forming the second noise reference signal includes subtracting the third and fourth weighted signals from the second secondary acoustic signal.

17. The non-transitory computer readable storage medium of claim 16, further comprising:

computing the first coefficient based on the primary acoustic signal and the first secondary acoustic signal;

computing the second coefficient based on the first and the second secondary acoustic signals;

computing the third coefficient based on the primary acoustic signal and the second secondary acoustic signal; and

computing the fourth coefficient based on the first and the second secondary acoustic signals.

18. A system for suppressing noise, comprising:

a primary microphone configured to receive a primary acoustic signal;

N secondary microphones configured to each receive a secondary acoustic signal; and

a noise reduction module executable by a processor to form a noise reference signal from each of the N secondary acoustic signals by suppressing N speech component sub-bands in each secondary acoustic signal, the N suppressed speech component sub-bands including a suppressed speech component sub-band correlated with a speech component sub-band in the primary acoustic signal and N−

1 suppressed speech component sub-bands correlated with each of the other secondary acoustic signals,

the noise reduction module further executable to reduce an energy level of a noise component sub-band in the primary acoustic signal based on the N noise reference signals.