Microphone array signal enhancement using mixture models

• US 20040002858A1
• Filed: 06/27/2002
• Published: 01/01/2004
• Est. Priority Date: 06/27/2002
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Deng, Li, Attias, Hagai
• Granted Patent: US 7,103,541 B2
• Time in Patent Office: Days
• US Class Current: 704/226
• CPC Class Codes: G10L 2021/02161 Number of inputs available containing the signal or the noise to be suppressed
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08

Abstract

A system and method facilitating signal enhancement utilizing mixture models is provided. The invention includes a signal enhancement adaptive system having a speech model, a noise model and a plurality of adaptive filter parameters. The signal enhancement adaptive system employs probabilistic modeling to perform signal enhancement of a plurality of windowed frequency transformed input signals received, for example, for an array of microphones. The signal enhancement adaptive system incorporates information about the statistical structure of speech signals. The signal enhancement adaptive system can be embedded in an overall enhancement system which also includes components of signal windowing and frequency transformation.

Claims

1. A signal enhancement adaptive system, comprising:

a speech model that characterizes statistical properties of speech;

a noise model that characterizes statistical properties of noise; and

,

a plurality of adaptive filter parameters utilized by the signal enhancement adaptive system to provide an enhanced signal output, the enhanced signal output being based, at least in part, upon a plurality of frequency transformed input signals, the plurality of adaptive filter parameters being modified based, at least in part, upon the speech model, the noise model and the enhanced signal output.

2. The signal enhancement adaptive system of claim 1, the speech model employing, at least in part, the equations:

3. The signal enhancement adaptive system of claim 1, the noise model employing, at least in part, the equation:

4. The signal enhancement adaptive system of claim 1, modification of at least one of the plurality of adaptive filter parameters being based upon a variational method.

5. The signal enhancement adaptive system of claim 1, modification of at least one of the plurality of adaptive filter parameters being, at least in part, upon the equation:

6. The signal enhancement adaptive system of claim 1, modification of at least one of the plurality of adaptive filter parameters being based upon a variational expectation maximization algorithm having an E-step and an M-step.

7. The signal enhancement adaptive system of claim 6, the E-step being based, at least in part, upon the equations:

8. The signal enhancement adaptive system of claim 1, the noise model being trained, at least in part, off-line.

9. The signal enhancement adaptive system of claim 1, the noise model being trained, at least in part, during a quiet period of at least one of the plurality of frequency transformed input signals.

10. The signal enhancement adaptive system of claim 1, the noise model being trained, at least in part, during operation of the signal enhancement adaptive model.

11. An overall signal enhancement system, comprising:

a frequency transformation component that receives windowed signal inputs, computes a frequency transform of the windowed signals, and provides outputs of frequency transformed windowed signals; and

,

a signal enhancement adaptive system having a speech model, a noise model and a plurality of adaptive filter parameters utilized to provide an enhanced signal output, the enhanced signal output being based, at least in part upon, the frequency transformed windowed signals, the plurality of adaptive filter parameters being modified based, at least in part, upon the speech model, the noise model and the enhanced signal output.

12. The system of claim 11, further comprising a windowing component that applies an N-point window to input signals and provides the windowed signal inputs to the frequency transformation component.

13. The system of claim 11, further comprising at least two audio input devices that provide the input signals.

14. The system of claim 13, at least one of the two audio input devices being a microphone.

15. The system of claim 11, the frequency transform being a Fast Fourier Transform.

16. A method for speech signal enhancement, comprising:

utilizing a signal enhancement adaptive model having a speech model and a noise model, providing an enhanced signal output based on a plurality of adaptive filter parameters; and

,

modifying at least one of the adaptive filter parameters based, at least in part, upon the speech model, the noise model and the enhanced signal output.

17. The method of claim 16, further comprising at least one of the following acts:

training the speech model,

training the noise model,

receiving input signals,

windowing the input signals, and,

performing a frequency transform of the windowed input signals.

18. A method for speech signal enhancement, comprising:

calculating an enhanced signal output based on a plurality of adaptive filter parameters;

for each frame and subband, calculating a conditional mean of the enhanced signal output;

for each frame and subband, calculating a conditional precision of the enhanced signal output;

for each frame and subband, calculating a conditional precision of the enhanced signal output;

calculating a conditional probability of a speech model;

calculating an autocorrelation of the enhanced signal output;

calculating a cross correlation of the enhanced signal output; and

,

modifying at least one of the plurality of adaptive filter parameters based on the autocorrelation and cross correlation of the enhanced signal output.

19. A data packet transmitted between two or more computer components that facilitates signal enhancement, the data packet comprising:

a data field comprising a plurality of adaptive filter parameters, at least one of the plurality of adaptive filter parameters having been modified based, at least in part, upon an enhanced signal output, a speech model and a noise model.

20. A computer readable medium storing computer executable components of a signal enhancement adaptive model, comprising:

a speech model component that models speech; and

,

a noise model component that models noise;

the signal enhancement adaptive mode utilizing a plurality of adaptive filter parameters to provide an enhanced signal output, the enhanced signal output being based, at least in part upon, a plurality of frequency transformed input signals, the plurality of adaptive filter parameters being modified based, at least in part, upon the speech model, the noise model and the enhanced signal output.

21. A signal enhancement system, comprising:

means for windowing a plurality of input signals;

means for frequency transforming the plurality of windowed input signals;

means for modeling speech;

means for modeling noise;

means for providing an enhanced signal output based, at least in part, upon the frequency transformed windowed signals; and

,

means for modifying the plurality of adaptive filter parameters, modification being based, at least in part, upon the means for modeling speech, the means for modeling noise and the enhanced signal output.