Relative noise ratio weighting techniques for adaptive noise cancellation

• US 6,766,292 B1
• Filed: 03/28/2000
• Issued: 07/20/2004
• Est. Priority Date: 03/28/2000
• Status: Expired due to Term

• Current Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Original Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Inventors: Chandran, Ravi, Dunne, Bruce E., Marchok, Daniel J.
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): Lerner, Martin
• Application Number:
  US09/535,844
• Time in Patent Office: 1,575 Days
• Field of Search: 704/205, 704/206, 704/210, 704/215, 704/225, 704/226, 704/224, 704/227, 704/200.1, 381/94.1, 381/94.2, 381/94.3, 381/94.7
• US Class Current: 704/224
• CPC Class Codes: G10L 21/0208 Noise filtering

Abstract

In order to enhance the quality of a communication signal comprising speech signal components due to speech and noise signal components due to noise, a filter divides the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components in a plurality of frequency bands. A calculator generates a plurality of weighting signals having weighting values corresponding to the frequency band signals. The weighting values represent at least approximations of the normalized powers of the noise signal components in the frequency band signals. The frequency band signals are altered in response to the weighting signals to generate weighted frequency band signals which are combined to generate a communication signal with enhanced quality.

Claims

1. In a communication system for processing a communication signal comprising speech signal components due to speech and noise signal components due to noise, apparatus for enhancing the quality of the communication signal comprising:

a filter arranged to divide the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components in a plurality of frequency bands; and

a calculator generating a plurality of weighting signals having weighting values corresponding to the frequency band signals, the weighting values derived from at least approximations of the normalized powers of the noise signal components in the frequency band signals, the weighting values varying monotonically with a first variation of the values of weight from a first value of weight at a first frequency to a second value of weight at a second frequency greater than the first frequency and the weighting values varying monotonically with a second variation of the values of weight opposite the first variation of the values of weight from the second value of weight to a third value of weight between the first value of weight and second value of weight at a frequency greater than the second frequency, combining the frequency band signals with the weighting signals to generate weighted frequency band signals, and combining the weighted frequency band signals to generate a communication signal with enhanced quality.

2. Apparatus, as claimed in claim 1, wherein the weighting values vary in accordance with at least an approximation of one or more characteristics of the noise signal component of the communication signal.

3. Apparatus, as claimed in claim 1, wherein the weighting values vary according to the spectral shape of the noise component of the communication signal.

4. Apparatus, as claimed in claim 1, wherein the weighting values are derived in part from the likelihood that the communication signal is derived at least in part from speech.

5. Apparatus, as claimed in claim 1, wherein the weighting signals vary according to a ratio of overall noisy signal power and overall background noise power of the communication signal.

6. Apparatus, as claimed in claim 1, wherein the approximations of the normalized powers of the noise signal components are derived from at least approximations of ratios of a power of one of the noise signal components in one of the frequency band signals and a maximum noise power value representing the maximum power of the noise signal components in one of a plurality of the frequency band signals.

7. Apparatus, as claimed in claim 1, wherein the filter forms a portion of the calculator.

8. Apparatus, as claimed in claim 1, wherein the calculator comprises a digital signal processor.

9. Apparatus, as claimed in claim 1, wherein the first variation of the values of weight comprises a decreasing variation and wherein the second variation of the values of weight comprises an increasing variation.

10. In a communication system for processing a communication signal comprising speech signal components due to speech and noise signal components due to noise, a method of enhancing the quality of the communication signal comprising:

dividing the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components;

generating a plurality of weighting signals having weighting values corresponding to the frequency band signals, the weighting values derived from at least approximations of the normalized powers of the noise signal components in the frequency band signals, varying the weighting values monotonically with a first variation of the values of weight from a first value of weight at a first frequency to a second value of weight at a second frequency greater than the first frequency and varying the weighting values monotonically with a second variation of the values of weight opposite the first variation of the values of weight from the second value of weight to a third value of weight between the first value of weight and second value of weight at a frequency greater than the second frequency;

combining the frequency band signals with the weighting signals to generate weighted frequency band signals; and

combining the weighted frequency band signals to generate a communication signal with enhanced quality.

11. A method, as claimed in claim 10, wherein the weighting values vary in accordance with at least an approximation of one or more characteristics of the noise signal component of the communication signal.

12. A method, as claimed in claim 10, wherein the weighting values vary according to the spectral shape of the noise component of the communication signal.

13. A method, as claimed in claim 10, wherein the weighting values are derived in part from the likelihood that the communication signal is derived at least in part from speech.

14. A method, as claimed in claim 10, wherein the weighting signals vary according to a ratio of overall noisy signal power and overall background noise power of the communication signal.

15. A method, as claimed in claim 10, wherein the approximations of the normalized powers of the noise signal components are derived from at least approximations of ratios of a power of one of the noise signal components in one of the frequency band signals and a maximum noise power value representing the maximum power of the noise signal components in one of a plurality of the frequency band signals.

16. A method, as claimed in claim 10, wherein the first variation of the values of weight comprises a decreasing variation and wherein the second variation of the values of weight comprises an increasing variation.

17. In a communication system for processing a communication signal comprising a speech signal component due to speech and a noise signal component due to noise, apparatus for enhancing the quality of the communication signal comprising:

means for dividing the communication signal into a plurality of frequency band signals representing a plurality of frequency bands;

a memory storing at least one weighting signal having weighting values varying in accordance with at least an approximation of one or more characteristics of the noise signal component of the communication signal, the weighting values varying monotonically with a first variation of the values of weight from a first value of weight at a first frequency to a second value of weight different from the first value of weight at a second frequency greater than the first frequency and the weighting values varying monotonically with a second variation of the values of weight opposite the first variation of the values of weight from the second value of weight to a third value of weight between the first value of weight and second value of weight at a frequency greater than the second frequency; and

a calculator combining the frequency band signals with the at least one weighting signal to generate weighted frequency band signals, and combining the weighted frequency band signals to generate a communication signal with enhanced quality.

18. Apparatus, as claimed in claim 17, wherein the weighting values vary according to the spectral shape of the noise component of the communication signal.

19. Apparatus, as claimed in claim 17, wherein the weighting values are derived in part from the likelihood that the communication signal is derived at least in part from speech.

20. Apparatus, as claimed in claim 17, wherein the weighting values vary according to a ratio of overall noisy signal power and overall background noise power of the communication signal.

21. Apparatus, as claimed in claim 17, wherein the first variation of the values of weight comprises a decreasing variation and wherein the second variation of the values of weight comprises an increasing variation.

22. In a communication system for processing a communication signal comprising a speech signal component due to speech and a noise signal component due to noise, a method of enhancing the quality of the communication signal comprising:

dividing said communication signal into a plurality of frequency band signals representing a plurality of frequency bands;

storing at least one weighting signal having weighting values varying in accordance with at least an approximation of one or more characteristics of the noise signal component of the communication signal, varying the weighting values monotonically with a first variation of the values of weight from a first value of weight at a first frequency to a second value of weight different from the first value of weight at a second frequency greater than the first frequency and varying the weighting values monotonically with a second variation of the values of weight opposite the first variation of the values of weight from the second value of weight to a third value of weight between the first value of weight and second value of weight at a frequency greater than the second frequency;

combining the frequency band signals with the at least one weighting signal to generate weighted frequency band signals; and

combining the weighted frequency band signals to generate a communication signal with enhanced quality.

23. A method, as claimed in claim 22, wherein the weighting values vary according to the spectral shape of the noise component of the communication signal.

24. A method, as claimed in claim 22, wherein the weighting values are derived at least in part from the likelihood that the communication signal is derived at least in part from speech.

25. A method, as claimed in claim 22, wherein the weighting values vary according to a ratio of overall noisy signal power and overall background noise power of the communication signal.

26. A method, as claimed in claim 22, wherein the first variation of the values of weight comprises a decreasing variation and wherein the second variation of the values of weight comprises an increasing variation.

27. In a communication system for processing a communication signal comprising speech signal components due to speech and noise signal components due to noise, apparatus for enhancing the quality of the communication signal comprising:

means for dividing the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components in a plurality of frequency bands, the frequency band signals defining a first group signal representing a first group of the frequency band signals and a second group signal representing a second group of the frequency band signals; and

a calculator generating a first group noise power signal having a first group noise power value related to the power of the noise signal component in the first group signal, generating a second group noise power signal having a second group noise power value related to the power of the noise signal component in the second group signal, generating a plurality of weighting signals having weighting values corresponding to the frequency band signals, at least one of the weighting signals having a weighting value derived from a ratio of the first group noise power value and the second group noise power value, altering the frequency band signals in response to the weighting signals to generate weighted frequency band signals, and combining the weighted frequency band signals to generate a communication signal with enhanced quality.

28. Apparatus, as claimed in claim 27, wherein the ratio is scaled by a first scaling factor.

29. Apparatus, as claimed in claim 27, wherein the second group of frequency band signals represents higher frequencies than the first group of frequency band signals.

30. Apparatus, as claimed in claim 27, wherein the first group of frequency band signals comprises a plurality of frequency band signals, wherein the second group of frequency band signals comprises a plurality of frequency band signals and wherein the calculator generates the first group noise power signal by summing the values of signals representing the power of the noise signal component in each of the frequency band signals in the first group and generates the second group noise power signal by summing the values of signals representing the power of the noise signal component in each of the frequency bands in the second group.

31. In a communication system for processing a communication signal comprising speech signal components due to speech and noise signal components due to noise, apparatus for enhancing the quality of the communication signal comprising:

means for dividing the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components in a plurality of frequency bands, the frequency band signals comprising a selected number of frequency band signals including at least a first frequency band signal and a second frequency band signal; and

a calculator generating an overall noise power signal having an overall noise power value related to the power of the noise components in at least some of the selected number of frequency band signals, generating a first band power signal having a first band power value related to the power of the noise components in the first frequency band signal and a second band power signal having a second band power value related to the power of the noise components in the second frequency band signal, generating a plurality of weighting signals having weighting values corresponding to the frequency band signals, a first of the weighting signals having a first weighting value derived from a ratio of the first band power value and a scaled value derived from the overall noise power value, and a second of the weighting signals having a second weighting value derived from a ratio of the second band power value and the scaled value, altering the first frequency band signal in response to the first weighting value to generate a first weighted frequency band signal, altering the second frequency band signal in response to the second weighting value to generate a second weighted frequency band signal, and combining the weighted frequency band signals to generate a communication signal with enhanced quality.

32. Apparatus, as claimed in claim 31, wherein the scaled value is derived from an average of the power of the noise components in the selected number of frequency bands.

33. Apparatus, as claimed in claim 31, wherein the calculator detects voice activity and generates a first signal indicating that the communication signal is derived at least in part from speech, and wherein the calculator is responsive to the first signal.

34. Apparatus, as claimed in claim 31, wherein the calculator further calculates an overall noisy signal power signal having a noisy signal power value related to the overall noisy signal power in the communication signal, wherein the calculator generates a noise signal ratio signal having a noise signal ratio value derived from a ratio of the overall noise power value and the overall noisy signal power value, and wherein the first weighting value and the second weighting value are derived in part from the noise signal ratio value.

35. Apparatus, as claimed in claim 31, wherein the means for dividing comprises a portion of the calculator.

36. Apparatus, as claimed in claim 31, wherein the calculator comprises a digital signal processor.

37. In a communication system for processing a communication signal comprising speech signal components due to speech and noise signal components due to noise, a method of enhancing the quality of the communication signal comprising:

dividing the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components and defining a first group signal representing a first group of the frequency band signals and a second group signal representing a second group of the frequency band signals;

generating a first group noise power signal having a first group noise power value related to the power of the noise signal component in the first group signal;

generating a second group noise power signal having a second group noise power value related to the power of the noise signal component in the second group signal;

generating a plurality of weighting signals having weighting values corresponding to the frequency band signals, at least one of the weighting signals having a weighting value derived from a ratio of the first group noise power value and the second group noise power value;

altering the frequency band signals in response to the weighting signals to generate weighted frequency band signals; and

combining the weighted frequency band signals to generate a communication signal with enhanced quality.

38. A method, as claimed in claim 37, wherein the ratio is scaled by a first scaling factor.

39. A method, as claimed in claim 37, wherein the second group of frequency band signals represents higher frequencies than the first group of frequency band signals.

40. A method, as claimed in claim 37, wherein the first group of frequency band signals comprises a plurality of frequency band signals, wherein the second group of frequency band signals comprises a plurality of frequency band signals and wherein the generating the first group noise power signal comprises summing the values of signals representing the power of the noise signal component in each of the frequency band signals in the first group and wherein the generating the second group noise power signal comprises summing the values of signals representing the power of the noise signal component in each of the frequency bands in the second group.

41. In a communication system for processing a communication signal comprising speech signal components due to speech and noise signal components due to noise, a method of enhancing the quality of the communication signal comprising:

dividing the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components, the frequency band signals comprising a selected number of frequency band signals including at least a first frequency band signal and a second frequency band signal;

generating an overall noise power signal having an overall noise power value related to the power of the noise signal components in at least some of the selected number of frequency band signals;

generating a first band power signal having a first band power value related to the power of the noise components in the first frequency band signal;

generating a second band power signal having a second band power value related to the power of the noise components in the second frequency band signal;

generating a plurality of weighting signals having weighting values corresponding to the frequency band signals, a first of the weighting signals having a first weighting value derived from a ratio of the first band power value and a scaled value derived from the overall noise power value, and a second of the weighting signals having a second weighting value derived from a ratio of the second band power value and the scaled value;

altering the first frequency band signal in response to the first weighting value to generate a first weighted frequency band signal;

altering the second frequency band signal in response to the second weighting value to generate a second weighted frequency band signal; and

combining the weighted frequency band signals to generate a communication signal with enhanced quality.

42. A method, as claimed in claim 41, wherein the scaled value is derived from an average of the power of the noise components.

43. A method, as claimed in claim 41, and further comprising:

generating a first signal indicating that the communication signal is derived at least in part from speech, and wherein the generating an overall noise power signal, generating a first band power signal and generating a second band power signal are responsive to the first signal.

44. A method, as claimed in claim 41, and further comprising:

calculating an overall noisy signal power signal having a noisy signal power value related to the overall noisy signal power in the communication signal; and

generating a noise signal ratio signal having a noise signal ratio value derived from a ratio of the overall noise power value and the overall noisy signal power value; and

wherein the first weighting value and the second weighting value are derived in part from the noise signal ratio value.