Speech detection with noise suppression based on principal components analysis

• US 6,230,122 B1
• Filed: 10/21/1998
• Issued: 05/08/2001
• Est. Priority Date: 09/09/1998
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Amador-Hernandez, Mariscela, Wu, Duanpei, Tanaka, Miyuki
• Primary Examiner(s): Korzuch, William R.
• Assistant Examiner(s): Storm, Donald L.
• Application Number:
  US09/176,178
• Time in Patent Office: 930 Days
• Field of Search: 704/233, 704/226, 704/227, 704/204
• US Class Current: 704/226
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 21/0232 Processing in the frequency domain

Abstract

A method for effectively suppressing background noise in a speech detection system comprises a filter bank for separating source speech data into discrete frequency sub-bands to generate filtered channel energy, and a noise suppressor for weighting the frequency sub-bands to improve the signal-to-noise ratio of the resultant noise-suppressed channel energy. The noise suppressor preferably includes a subspace module for using a Karhunen-Loeve transformation to create a subspace based on the background noise, a projection module for generating projected channel energy by projecting the filtered channel energy onto the created subspace, and a weighting module for applying calculated weighting values to the projected channel energy to generate the noise-suppressed channel energy.

Claims

1. A system for suppressing background noise in audio data, comprising:

a detector configured to perform a manipulation process on said audio data, said audio data including speech information, said detector including a speech detector configured to analyze and manipulate said speech information, wherein a first amplitude of said speech information is divided by a second amplitude of said background noise to generate a signal-to-noise ratio for said speech detector, said speech information including digital source speech data that is provided to said speech detector by an analog sound sensor and an analog-to-digital converter, wherein a filter bank generates filtered channel energy by separating said digital source speech data into discrete frequency channels, said speech detector comprising a noise suppressor, a projection module, and a weighting module, said noise suppressor including a subspace module for creating a subspace based upon said background noise, said projection module generating projected channel energy by projecting said filtered channel energy onto said subspace, said weighting module generating noise-suppressed channel energy by applying separate weighting values to each of said discrete frequency channels of said projected channel energy, said separate weighting values being proportional to said signal-to-noise ratios of said discrete frequency channels; and

a processor coupled to said system to control said detector and thereby suppress said background noise.

2. The system of claim 1 wherein said weighting module calculates a weighting value “

w_i”

for a channel “

i”

using a formula;

3. The system of claim 1 wherein said weighting module calculates a weighting value “

w_i”

for a channel “

i”

using a formula;

4. The system of claim 1 wherein said noise-suppressed channel energy “

E_T”

equals a summation of said projected channel energy from each of said discrete frequency channels “

E_i”

multiplied by a corresponding one of said weighting values “

w_i”

.

5. The system of claim 4 wherein said noise-suppressed channel energy “

E_T”

is defined by a formula;

6. The system of claim 1 wherein an endpoint detector analyzes said noise-suppressed channel energy to generate an endpoint signal.

7. The system of claim 6 wherein a recognizer analyzes said endpoint signal and feature vectors from a feature extractor to generate a speech detection result for said speech detector.

8. A method for suppressing background noise in audio data, comprising the steps of:

performing a manipulation process on said audio data using a detector, said audio data including speech information, said detector including a speech detector configured to analyze and manipulate said speech information, wherein a first amplitude of said speech information is divided by a second amplitude of said background noise to generate a signal-to-noise ratio for said speech detector, said speech information including digital source speech data that is provided to said speech detector by an analog sound sensor and an analog-to-digital converter, wherein a filter bank generates filtered channel energy by separating said digital source speech data into discrete frequency channels, said speech detector comprising a noise suppressor, a projection module, and a weighting module, said noise suppressor including a subspace module for creating a subspace based upon said background noise, said projection module generating projected channel energy by projecting said filtered channel energy onto said subspace, said weighting module generating noise-suppressed channel energy by applying separate weighting values to each of said discrete frequency channels of said projected channel energy, said separate weighting values being proportional to said signal-to-noise ratios of said discrete frequency channels; and

controlling said detector with a processor to thereby suppress said background noise.

9. The method of claim 8 wherein said weighting module calculates a weighting value “

w_i”

for a channel “

i”

using a formula;

10. The method of claim 8 wherein said weighting module calculates a weighting value “

w_i”

for a channel “

i”

using a formula;

11. The method of claim 8 wherein said noise-suppressed channel energy “

E_T”

equals a summation of said projected channel energy from each of said discrete frequency channels “

E_i”

multiplied by a corresponding one of said weighting values “

w_i”

.

12. The method of claim 11 wherein said noise-suppressed channel energy “

E_T”

is defined by a formula;

13. The method of claim 8 wherein an endpoint detector analyzes said noise-suppressed channel energy to generate an endpoint signal.

14. The method of claim 13 wherein a recognizer analyzes said endpoint signal and feature vectors from a feature extractor to generate a speech detection result for said speech detector.

15. A system for suppressing background noise in audio data, comprising:

a detector configured to perform a manipulation process on said audio data, said audio data including speech information, said detector including a speech detector configured to analyze and manipulate said speech information, wherein a first amplitude of said speech information is divided by a second amplitude of said background noise to generate a signal-to-noise ratio for said speech detector, said speech information including digital source speech data that is provided to said speech detector by an analog sound sensor and an analog-to-digital converter, wherein a filter bank generates filtered channel energy by separating said digital source speech data into discrete frequency channels, said speech detector comprising a noise suppressor, said noise suppressor including a subspace module, a projection module, and a weighting module, said subspace module creating a subspace based upon said background noise by using a Karhunen-Loeve transformation, said projection module generating projected channel energy by projecting said filtered channel energy onto said subspace, said weighting module generating noise-suppressed channel energy by applying separate weighting values to each of said discrete frequency channels of said projected channel energy, said separate weighting values being proportional to said signal-to-noise ratios of said discrete frequency channels; and

a processor coupled to said system to control said detector and thereby suppress said background noise.

16. A method for suppressing background noise in audio data, comprising the steps of:

performing a manipulation process on said audio data using a detector, said audio data including speech information, said detector including a speech detector configured to analyze and manipulate said speech information, wherein a first amplitude of said speech information is divided by a second amplitude of said background noise to generate a signal-to-noise ratio for said speech detector, said speech information including digital source speech data that is provided to said speech detector by an analog sound sensor and an analog-to-digital converter, wherein a filter bank generates filtered channel energy by separating said digital source speech data into discrete frequency channels, said speech detector comprising a noise suppressor, said noise suppressor including a subspace module, a projection module, and a weighting module, said subspace module creating a subspace based upon said background noise by using a Karhunen-Loeve transformation, said projection module generating projected channel energy by projecting said filtered channel energy onto said subspace, said weighting module generating noise-suppressed channel energy by applying separate weighting values to each of said discrete frequency channels of said projected channel energy, said separate weighting values being proportional to said signal-to-noise ratios of said discrete frequency channels; and

controlling said detector with a processor to thereby suppress said background noise.