Method and system for active noise cancellation

• US 20060069556A1
• Filed: 07/01/2005
• Published: 03/30/2006
• Est. Priority Date: 09/15/2004
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Nadjar, Hamid Sheikhzadeh, Brennan, Robert L., Schneider, Tood
• Granted Patent: US 8,280,065 B2
• Time in Patent Office: Days
• US Class Current: 704/229
• CPC Class Codes: G10K 11/17813 characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17875 using an error signal without a reference signal, e.g. pure feedback
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/101 One dimensional
• CPC Class Codes: G10K 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/3012 Algorithms
• CPC Class Codes: G10K 2210/3025 Determination of spectrum characteristics, e.g. FFT
• CPC Class Codes: G10K 2210/3027 Feedforward
• CPC Class Codes: G10K 2210/3051 Sampling, e.g. variable rate, synchronous, decimated or interpolated
• CPC Class Codes: G10K 2210/505 Echo cancellation, e.g. multipath-, ghost- or reverberation-cancellation
• CPC Class Codes: H03H 2021/0041 Subband decomposition
• CPC Class Codes: H03H 21/0027 filtering in the frequency domain

Abstract

A method and system for active noise cancellation is provided. The system employs subband processing, and preferably implements over-sampled filterbank. The system is applicable to adaptive noise cancellation, adaptive echo cancellation for portable listening devices, such as headsets and other similar listening devices.

Claims

1. A system for active noise cancellation, comprising:

a first over-sampled analysis filterbank for transferring a reference signal in a time-domain, which is associated with noise, into a plurality of subband reference signals in a frequency-domain;

a second over-sampled analysis filterbank for transferring a primary signal in the time-domain, which is associated with an acoustic signal and may be contaminated by the noise, into a plurality of subband primary signals in the frequency-domain;

a subband processing module for processing the subband reference signals, the subband primary signals or a combination thereof, and implementing one or more than one subband adaptive algorithm in the frequency-domain; and

an over-sampled synthesis filterbank for transferring the outputs of the subband processing module into a time-domain output signal.

2. A system as claimed in claim 1, wherein the over-sampled analysis filterbank is implemented by a Weighted-Overlap Add (WOLA) analysis filterbank, and the over-sampled synthesis filterbank is implemented by a WOLA synthesis filterbank.

3. A system as claimed in claim 1, wherein the subband processing module is provided for implementing one or more than one delayless subband adaptive algorithm.

4. A system as claimed in claim 1, wherein:

the over-sampled synthesis filterbank employs WOLA synthesis process to convert a plurality of subband adaptive filters from the subband processing module into a time-domain filter for filtering the reference signal in the time-domain.

5. A system as claimed in claim 4, wherein a time-domain output signal is provided by the output of the time-domain filter, or a combination of the output of the time-domain filter and the primary signal.

6. A system as claimed in claim 4, wherein:

a time-domain output signal is provided by the output of the time-domain filter and the primary signal, and

the time-domain output signal is provided as input to the second over-sampled analysis filterbank.

7. A system as claimed in claim 1, wherein the subband processing module is adaptive or re-programmable, and models one or more than one subband transfer function associated with an application of a listening device.

34. A system as claimed in claim 1, wherein the subband adaptive algorithm includes Filtered-X LMS (FX-LMS) algorithm.

35. A system as claimed in claim 3, wherein the delayless subband adaptive algorithm includes delayless Filtered-X LMS (FX-LMS) algorithm.

39. A method for implementing the system of claim 1.

47. A system as claimed in claim 3, wherein the delayless subband adaptive algorithm includes delayless Filtered-X LMS (FX-LMS) algorithm.

8. A system for active noise cancellation, comprising:

an over-sampled analysis filterbank for transferring a primary signal in a time-domain, which is associated with an acoustic signal and may be contaminated by noise, into a plurality of subband primary signals in a frequency-domain;

a subband processing module for the subband primary signals and implementing one or more than one subband adaptive algorithm in frequency-domain; and

an over-sampled synthesis filterbank for transferring the outputs of the subband processing module into a time-domain output signal.

9. A system as claimed in claim 8, wherein the over-sampled analysis filterbank is implemented by a WOLA analysis filterbank, and the over-sampled synthesis filterbank is implemented by a WOLA synthesis filterbank.

10. A system as claimed in claim 8, wherein the subband processing module is adaptive or re-programmable, and models one or more than one subband transfer function associated with an application of a listening device.

44. A system as claimed in claim 10, wherein the subband adaptive algorithm includes Filtered-X LMS (FX-LMS) algorithm.

11. A system for active noise cancellation, comprising:

a first analysis filter bank for transferring a reference signal in a time-domain into a plurality of subband reference signals in a frequency-domain;

a second analysis filter bank for transferring a primary signal in the time-domain, which is associated with an acoustic signal and may be contaminated by noise, into a plurality of subband primary signals in the frequency-domain;

a subband estimator for modeling subband acoustic transfer function for the subband reference signals;

a subband adaptive filter for providing a plurality of subband output signals in response to the subband reference signals;

an adjustor for adjusting the subband adaptive filter in response to the subband primary signals and the modeling for the subband reference signals; and

a synthesis filter bank for transferring the subband output signals to a time-domain output signal.

12. A system as claimed in claim 11, wherein:

the synthesis filter bank employs WOLA synthesis process to convert the subband adaptive filter into a time-domain filter for filtering the reference signal in the time-domain.

15. A system as claimed in claim 11, wherein the system is implemented by an over-sampled filterbank.

16. A system as claimed in claim 11, wherein the system is implemented by a WOLA filterbank.

36. A system as claimed in claim 11, wherein the adjustor implements NMSL adaptation algorithm.

13. A system for active noise cancellation, comprising:

an analysis filter bank for transferring a primary signal in a time-domain into a plurality of subband primary signals in a frequency-domain;

a subband filter bank for providing a plurality of subband output signals in response to a plurality of subband reference signals;

a synthesis filter bank for transferring the subband output signals into a time-domain output signal; and

a feed-back loop for generating the subband reference signals, including;

a first subband estimator for modeling subband acoustic transfer function for the subband output signals;

a signal path for providing the subband reference signals in response to the subband primary signals and the modeling for the subband output signals;

a second subband estimator for modeling subband acoustic transfer function for the subband reference signals; and

an adjustor for adjusting the subband adaptive filter in response to the subband primary signals and the modeling for the subband reference signals.

40. A system as claimed in claim 13, wherein the system is implemented by an over-sampled filterbank.

41. A system as claimed in claim 13, wherein the system is implemented by a WOLA filterbank.

52. A system as claimed in claim 13, wherein the adjustor implements NMSL adaptation algorithm.

14. A system for active noise cancellation, comprising:

a first analysis filter bank for transferring a primary signal in a time-domain into a plurality of subband primary signals in a frequency-domain;

a time-domain filter bank for providing a time-domain output signal in response to a reference signal in the time-domain;

a feed-back loop for generating the reference signal, including;

a first subband estimator for modeling subband acoustic transfer function for the time-domain output signal,

a signal path for providing the reference signal in the time-domain in response to a primary signal in the time-domain and the modeling for the time-domain output signal,

a second subband estimator for modeling subband acoustic transfer function for the subband reference signal,

a second analysis filter bank for transferring the primary signal into a plurality of subband primary signals in the frequency-domain,

an adjustor for adjusting the subband adaptive filter in response to the subband primary signals and the modeling for the reference signal, and

a synthesis filter bank for converting the subband adaptive filter to the time-domain filter bank for filtering the reference signal.

42. A system as claimed in claim 14, wherein the system is implemented by an over-sampled filterbank.

43. A system as claimed in claim 14, wherein the system is implemented by a WOLA filterbank.

17. A system for active noise cancellation, comprising:

an analog active noise cancellation (ANC) system for performing an active noise cancellation to a primary signal in a time-domain, which is associated with an acoustic signal and may be contaminated by noise;

a first over-sampled analysis filterbank for transferring a reference signal in the time-domain into a plurality of subband reference signals in a frequency-domain, the reference signal in the time-domain being associated with the noise;

a second over-sampled analysis filterbank for transferring the primary signal in the time-domain into a plurality of subband primary signals in the frequency-domain;

a subband processing module for processing the subband reference signals, the subband primary signals or a combination thereof, and for adjusting one or more parameters of the analog ANC system;

an over-sampled synthesis filterbank for performing conversion on the outputs of the subband processing module from the frequency-domain to the time-domain.

18. A system as claimed in claim 17, wherein the over-sampled analysis filterbank is implemented by a WOLA analysis filterbank, and the over-sampled synthesis filterbank is implemented by a WOLA synthesis filterbank.

19. A system as claimed in claim 18, wherein the subband processing module implements one or more than one subband adaptive algorithm.

20. A system as claimed in claim 18, wherein the subband processing module is provided for implementing one or more than one delayless subband adaptive algorithm.

21. A system as claimed in claim 20, wherein:

the over-sampled synthesis filterbank employing WOLA synthesis process to convert a plurality of subband adaptive filters from the subband processing module into a time-domain filter for filtering the reference signal in the time-domain.

22. A system as claimed in claim 21, wherein a time-domain output signal is provided by the output of the time-domain filter or a combination of the output of the time-domain filter and the primary signal.

23. A system as claimed in claim 21, wherein:

a time-domain output signal is provided by the output of the time-domain filter and the primary signal, and

the time-domain output signal is provided to the second over-sampled analysis filterbank.

24. A system as claimed in claim 17, wherein the subband processing module is adaptive or re-programmable, and models one or more than one subband transfer function associated with an application of a listening device.

37. A system as claimed in claim 17, wherein the adjustable parameters of the analog ANC system include loop-filter frequency, loop-gain, similar parameters or combinations thereof.

38. A system as claimed in claim 17, wherein the subband processing module is capable of modeling one or more than one acoustic transfer function, a transfer function for a microphone, a transfer function for a loudspeaker, or combinations thereof.

45. A system as claimed in claim 19, wherein the subband adaptive algorithm includes Filtered-X LMS (FX-LMS) algorithm.

48. A system as claimed in claim 20, wherein the delayless subband adaptive algorithm includes delayless Filtered-X LMS (FX-LMS) algorithm.

25. A system for active noise cancellation, comprising:

an analog active noise cancellation (ANC) system for performing an active noise cancellation to a primary signal in a time-domain, which is associated with an acoustic signal and may be contaminated by noise;

an over-sampled analysis filterbank for transferring the primary signal in the time-domain into a plurality of subband primary signals in a frequency-domain;

a subband processing module for processing the subband primary signals and for adjusting one or more than one parameter of the analog ANC system;

an over-sampled synthesis filterbank for transferring the outputs of the subband processing module into an output signal in the time-domain.

26. A system as claimed in claim 25, wherein the over-sampled analysis filterbank is implemented by a WOLA analysis filterbank, and the over-sampled synthesis filterbank is implemented by a WOLA synthesis filterbank.

27. A system as claimed in claim 25, wherein the subband processing module implements one or more than one subband adaptive algorithm.

28. A system as claimed in claim 25, wherein the subband processing module is provided for implementing one or more than one delayless subband adaptive algorithm.

29. A system as claimed in claim 25, wherein the subband processing module is adaptive or re-programmable, and models one or more than one subband transfer functions associated with an application of a listening device.

46. A system as claimed in claim 27, wherein the subband adaptive algorithm includes Filtered-X LMS (FX-LMS) algorithm.

49. A system as claimed in claim 28, wherein the delayless subband adaptive algorithm includes delayless Filtered-X LMS (FX-LMS) algorithm.

53. A system as claimed in claim 25, wherein the adjustable parameters of the analog ANC system include loop-filter frequency, loop-gain, similar parameters or combinations thereof.

55. A system as claimed in claim 25, wherein the subband processing module is capable of modeling one or more than one acoustic transfer function, a transfer function for a microphone, a transfer function for a loudspeaker, or combinations thereof.

30. A system for active noise cancellation, comprising:

a first WOLA analysis filterbank for transferring a reference signal in a time-domain, which is associated with noise, into a plurality of subband reference signals in a frequency-domain;

a second WOLA analysis filterbank for transferring a primary signal in the time-domain, which is associated with an acoustic signal and may be contaminated by the noise, into a plurality of subband primary signals;

a subband adaptive processing module for processing the output of the first WOLA analysis filterbank, the output of the second WOLA analysis filterbank or a combination thereof, and providing a plurality of subband adaptive filters; and

a WOLA synthesis filterbank for synthesizing the subband adaptive filters to provide a time-domain filter for filtering the reference signal in the time-domain.

31. A system as claimed in claim 30, wherein the subband adaptive processing module is provided for implementing one or more than one delayless subband adaptive algorithm.

50. A system as claimed in claim 31, wherein the delayless subband adaptive algorithm includes delayless Filtered-X LMS (FX-LMS) algorithm.

54. A system as claimed in claim 30, wherein the adjustable parameters of the analog ANC system include loop-filter frequency, loop-gain, similar parameters or combinations thereof.

56. A system as claimed in claim 30, wherein the subband processing module is capable of modeling one or more than one acoustic transfer function, a transfer function for a microphone, a transfer function for a loudspeaker, or combinations thereof.

32. A system for active noise cancellation, comprising:

a WOLA analysis filterbank for transferring a primary signal in a time-domain, which is associated with an acoustic signal and may be contaminated by noise, into a plurality of subband primary signals;

a subband adaptive processing module for processing the output of the WOLA analysis filterbank, and providing a plurality of subband adaptive filters; and

a WOLA synthesis filterbank for synthesizing the subband adaptive filters to provide a time-domain filter for filtering a reference signal in the time-domain associated with the noise.

33. A system as claimed in claim 32, wherein the subband adaptive processing module is provided for implementing one or more than one delayless subband adaptive algorithm.

51. A system as claimed in claim 33, wherein the delayless subband adaptive algorithm includes delayless Filtered-X LMS (FX-LMS) algorithm.