System and method for utilizing inter-microphone level differences for speech enhancement

• US 20070154031A1
• Filed: 01/30/2006
• Published: 07/05/2007
• Est. Priority Date: 01/05/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Audience Corporation
• Inventors: Avendano, Carlos, Santos, Peter
• Granted Patent: US 8,345,890 B2
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 2410/01 Noise reduction using microphones having different directional characteristics
• CPC Class Codes: H04R 2430/20 Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic H04R2203/12 takes precedence
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits
• 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 utilizing inter-microphone level differences to attenuate noise and enhance speech are provided. In exemplary embodiments, energy estimates of acoustic signals received by a primary microphone and a secondary microphone are determined in order to determine an inter-microphone level difference (ILD). This ILD in combination with a noise estimate based only on a primary microphone acoustic signal allow a filter estimate to be derived. In some embodiments, the derived filter estimate may be smoothed. The filter estimate is then applied to the acoustic signal from the primary microphone to generate a speech estimate.

Claims

1. A method for enhancing speech, comprising:

receiving a primary acoustic signal at a primary microphone and a secondary acoustic signal at a secondary microphone;

determining a filter estimate during a frame, the filter estimate based on a noise estimate of the primary acoustic signal, an energy estimate of the primary acoustic signal, and an inter-microphone level difference based on the primary and secondary acoustic signals; and

applying the filter estimate to the primary acoustic signal to produce a speech estimate.

2. The method of claim 1 further comprising determining an energy estimate for each of the acoustic signals during the frame.

3. The method of claim 2 wherein the energy estimate of the primary acoustic signal is approximated as E₁(t, ω

)=λ

_E|X₁(t,ω

)|²+(1−

λ

_E)E₁(t−

1, ω

).

4. The method of claim 2 wherein the energy estimate of the secondary acoustic signal is approximated as E₂(t,ω

)=λ

_E|X₂(t,ω

)|²+(1−

λ

_E)E₂(t −

1, ω

).

5. The method of claim 2 further comprising using the energy estimates to determine the inter-microphone level difference for the frame.

6. The method of claim 5 wherein the inter-microphone level difference is approximated by

$\mathrm{ILD}$

( t , ω

) = [ 1 - 2 ⁢

 

⁢

E 1 ⁢

( t , ω

) ⁢

E 2 ⁡

( t , ω

) E 1 2 ⁡

( t , ω

) + E 2 2 ⁡

( t , ω

) ] * sign ⁢

 

⁢

( E 1 ⁡

( t , ω

) - E 2 ⁡

( t , ω

) ) .

7. The method of claim 5 wherein the inter-microphone level difference is approximated by

$\mathrm{ILD}$

( t , ω

) = E 1 ⁡

( t , ω

) - E 2 ⁢

 

⁡

( t , ω

) E 1 ⁡

( t , ω

) + E 2 ⁡

( t , ω

) .

8. The method of claim 1 wherein the noise estimate is based on an energy estimate of the primary acoustic signal and the inter-microphone level difference.

9. The method of claim 8 wherein the noise estimate is approximated as N(t, ω

)=λ

₁(t, ω

)E₁(t, ω

)+(1−

λ

₁(t, ω

))min[N(t−

1, ω

), E₁(t, ω

)].

10. The method of claim 1 further comprising smoothing the filter estimate prior to applying the filter estimate to the primary acoustic signal.

11. The method of claim 10 wherein the smoothing is approximated as M(t,ω

)=λ

₁(t,ω

)W(t, ω

)+(131 λ

_s(t,ω

))M(t−

1, ω

).

12. The method of claim 1 further comprising converting the speech estimate to a time domain.

13. The method of claim 1 further comprising outputting the speech estimate to a user.

14. The method of claim 1 wherein the filter estimate is based on a Weiner filter.

15. A system for enhancing speech on a device, comprising:

a primary microphone configured to receive a primary acoustic signal;

a secondary microphone located a distance away from the primary microphone and configured to receive a secondary acoustic signal; and

an audio processing engine configured to enhance speech received at the primary microphone, the audio processing engine comprising

a noise estimate module configured to determine a noise estimate for the primary acoustic signal based on an energy estimate of the primary acoustic signal and an inter-microphone level difference; and

a filter module configured to determine a filter estimate to be applied to the primary acoustic signal to generate a filtered acoustic signal, the filter estimate based on the noise estimate of the primary acoustic signal, the energy estimate of the primary acoustic signal, and the inter-microphone level difference.

16. The system of claim 15 wherein the audio processing engine further comprises an energy module configured to determine energy estimates for a frame of the primary and secondary acoustic signals.

17. The system of claim 15 wherein the audio processing engine further comprises an inter-microphone level difference module configured to determine the inter-microphone level difference.

18. The system of claim 15 wherein the audio processing engine further comprises a filter smoothing module configured to smooth the filter estimate prior to applying the filter estimate to the primary acoustic signal.

19. The system of claim 15 wherein the audio processing engine further comprises a masking module configured to determine the speech estimate.

20. A computer readable medium having embodied thereon a program, the program being executable by a machine to perform a method for enhancing speech on a device, the method comprising:

receiving a primary acoustic signal at a primary microphone and a secondary acoustic signal at a secondary microphone;

determining an energy estimate over a frame for each of the acoustic signals;

using the energy estimates to determine an inter-microphone level difference for the frame;

generating a noise estimate based on the energy estimate of the primary acoustic signal, the energy estimate of the primary acoustic signal, and the inter-microphone level difference;

calculating a filter estimate based on the noise estimate and the inter-microphone level difference; and

applying the filter estimate to the primary acoustic signal to produce a speech estimate.