Small array microphone for acoustic echo cancellation and noise suppression

• US 7,003,099 B1
• Filed: 02/21/2003
• Issued: 02/21/2006
• Est. Priority Date: 11/15/2002
• Status: Active Grant

• Current Assignee: Fortemedia, Inc.
• Original Assignee: Fortemedia, Inc.
• Inventors: Zhang, Ming, Pai, Wan-Chieh
• Primary Examiner(s): Swerdlow, Daniel
• Application Number:
  US10/371,150
• Time in Patent Office: 1,096 Days
• Field of Search: 37938801-38802, 379/392.01, 37940602-40603, 379/406.05, 37940612-40614, 381/94.3, 381/94.7
• US Class Current: 379/406.03
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

Techniques for canceling echo and suppressing noise using an array microphone and signal processing. In one system, at least two microphones form an array microphone and provide at least two microphone input signals. Each input signal may be processed by an echo canceller unit to provide a corresponding intermediate signal having some echo removed. An echo cancellation control unit receives the intermediate signals and derives a first gain used for echo cancellation. A noise suppression control unit provides at least one control signal used for noise suppression based on background noise detected in the intermediate signals. An echo cancellation and noise suppression unit derives a second gain based on the control signal(s), cancels echo in a designated intermediate signal based on the first gain, and suppresses noise in this intermediate signal based on the second gain. The signal processing may be performed in the frequency domain.

Claims

1. An echo cancellation and noise suppression system comprising:

an echo cancellation control unit operative to derive a first gain used for echo cancellation based on at least two intermediate signals for at least two microphones of an array microphone;

a noise estimator operative to provide a first signal indicative of background noise detected in the intermediate signals;

a noise suppression control unit operative to provide at least one control signal for noise suppression based on the first signal; and

an echo cancellation and noise suppression unit operative to cancel echo and suppress noise in a designated one of the intermediate signals based on the first gain and the at least one control signal.

2. The system of claim 1, wherein the echo cancellation and noise suppression unit is further operative to derive a second gain used for noise suppression.

3. The system of claim 1, wherein the intermediate signals are frequency-domain signals, and wherein the echo cancellation and noise suppression unit is operative to cancel echo and suppress noise in the frequency domain.

4. The system of claim 3, wherein the echo cancellation and noise suppression unit is operative to cancel echo and suppress noise for each of a plurality of frequency bins.

5. The system of claim 1, wherein the first gain is derived based on powers of the intermediate signals and cross-correlation between the intermediate signals.

6. The system of claim 2, wherein the second gain is derived based on signal power of the designated intermediate signal and noise powers of remaining ones of the intermediate signals.

7. The system of claim 1, wherein the echo cancellation and noise suppression unit is operative to suppress nonlinear echo and large amount of noise in low signal-to-noise ratio (SNR) environment.

8. The system of claim 1, wherein the at least two microphones are placed in close proximity to each other and include an omni-directional microphone and a uni-directional microphone having a main lobe facing a voice source.

9. The system of claim 1, wherein the at least two microphones are placed in close proximity to each other and include at least two uni-directional microphones, wherein one of the uni-directional microphones has a main lobe facing a voice source and another one of the uni-directional microphone has a main lobe facing away from the voice source.

10. An echo cancellation and noise suppression system comprising:

at least two microphones forming an array microphone and operative to provide at least two microphone input signals;

an echo cancellation control unit operative to receive at least two intermediate signals derived from the microphone input signals and provide a first gain used for echo cancellation;

a noise estimator operative to detect for background noise in the intermediate signals and provide a first signal indicative of the detected background noise;

a noise suppression control unit operative to receive the first signal and determine at least one control signal for noise suppression; and

an echo cancellation and noise suppression unit operative to derive a second gain based in part on the at least one control signal and to cancel echo and suppress noise in a designated one of the intermediate signals based on the first and second gains.

11. The system of claim 10, further comprising:

a first voice activity detector operative to detect for far-end activity, and wherein the echo cancellation is performed based on the detected far-end activity.

12. The system of claim 10, further comprising:

a second voice activity detector operative to detect for activity in the microphone input signals, and wherein the noise suppression is performed based on the detected near-end activity.

13. The system of claim 10, further comprising:

at least two echo canceller units each operative to process a respective microphone input signal from one of the at least two microphones and provide one of the at least two intermediate signals having a portion of echo in the microphone input signal canceled.

14. The system of claim 10, wherein the intermediate signals are frequency-domain signals, and wherein the echo cancellation and noise suppression unit is operative to cancel echo and suppress noise in the frequency domain.

15. The system of claim 10, wherein the at least two microphones include an omni-directional microphone and a uni-directional microphone having a main lobe facing a voice source.

16. The system of claim 10, wherein the at least two microphones include at least two uni-directional microphones, wherein one of the uni-directional microphones has a main lobe facing a voice source and another one of the uni-directional microphone.

17. An apparatus suitable for canceling echo and suppressing noise, comprising:

means for deriving a first gain used for echo cancellation based on at least two intermediate signals for at least two microphones of an array microphone;

means for deriving a second gain used for noise suppression based on detected background noise in the intermediate signals;

means for canceling echo in a designated one of the intermediate signals based on the first gain; and

means for suppressing noise in the designated intermediate signal based on the second gain.

18. The apparatus of claim 17, further comprising:

means for detecting background noise in the intermediate signals.

19. The apparatus of claim 17, further comprising:

means for canceling echo in each of at least two input signals from the at least two microphones to provide a corresponding intermediate signal.

20. A method of canceling echo and suppressing noise, comprising:

deriving a first gain used for echo cancellation based on at least two intermediate signals for at least two microphones of an array microphone;

deriving a second gain used for noise suppression based on detected background noise in the intermediate signals;

canceling echo in a designated one of the at least two intermediate signals based on the first gain; and

suppressing noise in the designated intermediate signal based on the second gain.

21. The method of claim 20, further comprising:

detecting for far-end activity, and wherein the canceling is performed based on the detected far-end activity.

22. The method of claim 20, further comprising:

detecting for near-end activity in the intermediate signals, and wherein the suppressing is performed based on the detected near-end activity.

23. The method of claim 20, further comprising:

receiving at least two microphone input signals from the at least two microphones; and

canceling a portion of echo in the at least two microphone input signals to provide the intermediate signals having residual echo.