Off-line path modeling circuitry and method for off-line feedback path modeling and off-line secondary path modeling

• US 5,991,418 A
• Filed: 12/17/1997
• Issued: 11/23/1999
• Est. Priority Date: 12/17/1996
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Kuo, Sen M.
• Primary Examiner(s): Lee, Ping
• Application Number:
  US08/992,933
• Time in Patent Office: 706 Days
• Field of Search: 381/71.11, 381/71.14, 381/71.5, 381/71.8, 381/71.12, 364/724.18, 364/724.19, 708/322
• US Class Current: 381/71.11
• CPC Class Codes: G10K 11/17817 between the output signals and the error signals, i.e. secondary path
• CPC Class Codes: G10K 11/17819 between the output signals and the reference signals, e.g. to prevent howling
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/30232 Transfer functions, e.g. impulse response
• CPC Class Codes: G10K 2210/3027 Feedforward
• CPC Class Codes: G10K 2210/3041 Offline

Abstract

An off-line modeling system (50) is provided for modeling a feedback path and a secondary path by calculating feedback neutralization filter taps and secondary path compensation filter taps. The off-line modeling system (50) includes a reference sensor (16), a secondary source (18), an error sensor (20), and an off-line modeling circuitry (10). The reference sensor (16) receives a noise signal and a feedback signal (22) and generates a primary signal x(n) in response. The secondary source (18) receives a modeling signal v(n) and provides the modeling signal v(n) to the feedback path and the secondary path. The error sensor (20) receives a residual signal generates an error signal e(n). The off-line modeling circuitry (10) receives the primary signal x(n) and the error signal e(n) and generates the modeling signal v(n) while modeling the feedback path and the secondary path.

Claims

1. An off-line modeling system for modeling a feedback path and a secondary path, the off-line modeling system comprising:

a reference sensor operable to receive a noise signal and a feedback signal and to generate a primary signal in response;

a secondary source operable to receive a modeling signal and to provide the modeling signal through the feedback path and the secondary path;

an error sensor operable to receive a residual signal and to generate an error signal in response; and

an off-line modeling circuitry for modeling the feedback path and the secondary path including;

a modeling signal generator operable to generate the modeling signal,

a feedback path signal discrimination circuitry operable to receive the primary signal and to generate a modified modeling feedback signal, said feedback path signal discrimination circuitry including;

a decorrelation delay unit operable to delay the primary signal and to generate a delayed output signal that corresponds to a delayed primary signal,

an adaptive discrimination filter operable to receive the delayed output signal and the modified modeling feedback signal and to filter the delayed output signal to generate a predicted noise signal, and

a first summing junction operable to subtract the predicted noise signal from the primary signal to generate the modified modeling feedback signal,

a feedback path modeling adaptive filter operable to receive the modeling signal and a feedback path modeling error signal and to filter the modeling signal to generate a first output signal, the feedback path modeling adaptive filter operable to calculate feedback neutralization filter taps,

a second summing junction operable to subtract the first output signal from the modified modeling feedback signal to generate the feedback path modeling error signal which is provided to a first adaptive algorithm used by the feedback path modeling adaptive filter,

a secondary path signal discrimination circuitry operable to receive the error signal and to generate a modified modeling secondary path signal,

a secondary path modeling adaptive filter operable to receive the modeling signal and a secondary path modeling error signal and to filter the modeling signal to generate a second output signal, the secondary path modeling adaptive filter operable to calculate secondary path compensation filter taps, and

a third summing junction operable to subtract the second output signal from the modified modeling secondary path signal to generate the secondary path modeling error signal which is provided to a second adaptive algorithm used by the secondary path modeling adaptive filter.

2. The off-line modeling system of claim 1, further comprising:

a first interface circuit operable to convert the primary signal in the analog domain to the digital domain and to provide the primary signal to the off-line modeling circuitry in the digital domain;

a second interface circuit operable to convert a secondary signal in the digital domain to the analog domain and to provide the secondary signal to the secondary source in the analog domain; and

a third interface circuit operable to convert the residual signal in the analog domain to the digital domain to generate the error signal in response, the third interface circuit operable to provide the error signal to the off-line modeling circuitry in the digital domain.

3. The off-line modeling system of claim 1, wherein the off-line modeling circuitry uses digital circuitry.

4. The off-line modeling system of claim 1, wherein the reference sensor is a microphone, and the secondary source is a speaker.

5. The off-line modeling system of claim 1, wherein the calculated feedback neutralization filter taps and the calculated secondary path compensation filter taps are stored in computer memory after being calculated.

6. The off-line modeling system of claim 1, wherein the secondary path signal discrimination circuitry includes:

a decorrelation delay unit operable to delay the error signal and to generate a delayed output signal that corresponds to a delayed error signal;

an adaptive discrimination filter operable to receive the delayed output signal and the modified modeling secondary path signal and to filter the delayed output signal to generate a predicted noise signal; and

a fourth summing junction operable to subtract the predicted noise signal from the error signal to generate the modified modeling secondary path signal.

7. The off-line modeling system of claim 6, wherein the delay of the decorrelation delay unit is a programmable delay.

8. The off-line modeling system of claim 6, wherein the delay is equal to or greater than the delay of the secondary path being modeled.

9. An off-line modeling circuitry for modeling the feedback path and the secondary path of an active noise control system, the off-line modeling circuitry comprising:

a modeling signal generator operable to generate the modeling signal;

a feedback path signal discrimination circuitry operable to receive a primary signal and to generate a modified modeling feedback signal, said feedback path signal discrimination circuitry including;

a decorrelation delay unit operable to delay the primary signal and to generate a delayed output signal that corresponds to a delayed primary signal,

an adaptive discrimination filter operable to receive the delayed output signal and the modified modeling feedback signal and to filter the delayed output signal to generate a predicted noise signal, and

a first summing junction operable to subtract the predicted noise signal from the primary signal to generate the modified modeling feedback signal;

a feedback path modeling adaptive filter operable to receive the modeling signal and a feedback path modeling error signal and to filter the modeling signal to generate a first output signal, the feedback path modeling adaptive filter operable to calculate feedback neutralization filter taps;

a second summing junction operable to subtract the first output signal from the modified modeling feedback signal to generate the feedback path modeling error signal which is provided to a first adaptive algorithm used by the feedback path modeling adaptive filter;

a secondary path signal discrimination circuitry operable to receive an error signal and to generate a modified modeling secondary path signal;

a secondary path modeling adaptive filter operable to receive the modeling signal and a secondary path modeling error signal and to filter the modeling signal to generate a second output signal, the secondary path modeling adaptive filter operable to calculate secondary path compensation filter taps; and

a third summing junction operable to subtract the second output signal from the modified modeling secondary path signal to generate the secondary path modeling error signal which is provided to a second adaptive algorithm used by the secondary path modeling adaptive filter.

10. The off-line modeling circuitry of claim 9, further comprising a memory for storing the feedback neutralization filter taps and the secondary path compensation filter taps.

11. The off-line modeling circuitry of claim 9, wherein the first adaptive algorithm used by the feedback path modeling adaptive filter is operable to calculate the feedback neutralization filter taps by minimizing the mean-square value of the feedback path modeling error signal, and wherein the second adaptive algorithm used by the secondary path modeling adaptive filter is operable to calculate the secondary path compensation filter taps by minimizing the mean-square value of the secondary path modeling error signal.

12. The off-line modeling circuitry of claim 9, wherein the delay of the decorrelation delay unit is a programmable delay.

13. The off-line modeling circuitry of claim 9, wherein the delay is equal to or greater than the delay of the feedback path being modeled.

14. The off-line modeling circuitry of claim 9, wherein the secondary path signal discrimination circuitry includes:

a decorrelation delay unit operable to delay the error signal and to generate a delayed output signal that corresponds to a delayed error signal;

an adaptive discrimination filter operable to receive the delayed output signal and the modified modeling secondary path signal and to filter the delayed output signal to generate a predicted noise signal; and

a third summing junction operable to subtract the predicted noise signal from the error signal to generate the modified modeling secondary path signal.

15. The off-line modeling circuitry of claim 14, wherein the delay of the decorrelation delay unit is a programmable delay.

16. The off-line modeling circuitry of claim 14, wherein the delay is equal to or greater than the delay of the secondary path being modeled.

17. The off-line modeling circuitry of claim 9, wherein the modeling signal generator is a white noise generator.

18. The off-line modeling circuitry of claim 9, wherein the error signal provided to the secondary path signal discrimination circuitry is provided from an error sensor.

19. A method for off-line feedback path modeling and off-line secondary path modeling comprising the steps of:

providing a modeling signal to an environment;

receiving a primary signal in response to providing the modeling signal to the environment;

receiving an error signal in response to providing the modeling signal to the environment;

generating a modified modeling feedback signal using the primary signal by

generating a first delayed output signal corresponding to a delayed primary signal using a first decorrelation delay unit,

filtering the first delayed output signal to generate a first predicted noise signal from the first delayed output signal and the modified modeling feedback signal using an adaptive discrimination filter, and

subtracting the first predicted noise signal from the primary signal to generate the modified modeling feedback signal;

generating feedback neutralization filter taps using an adaptive filter and the modified modeling feedback signal;

generating a modified modeling secondary path signal using the error signal by

generating a second delayed output signal corresponding to a delayed secondary signal using a second decorrelation delay unit,

filtering the second delayed output signal to generate a second predicted noise signal from the delayed output signal and the modified modeling feedback signal using an adaptive discrimination filter, and

subtracting the second predicted noise signal from the secondary signal to generate the modified modeling secondary path signal; and

generating secondary path compensation filter taps using an adaptive filter and the modified modeling secondary path signal.

20. An off-line modeling system for modeling a feedback path and a secondary path, the off-line modeling system comprising:

a reference sensor operable to receive a noise signal and a feedback signal and to generate a primary signal in response;

a secondary source operable to receive a modeling signal and to provide the modeling signal through the feedback path and the secondary path;

an error sensor operable to receive a residual signal and to generate an error signal in response; and

an off-line modeling circuitry for modeling the feedback path and the secondary path including;

a modeling signal generator operable to generate the modeling signal,

a feedback path signal discrimination circuitry operable to receive the primary signal and to generate a modified modeling feedback signal;

a feedback path modeling adaptive filter operable to receive the modeling signal and a feedback path modeling error signal and to filter the modeling signal to generate a first output signal, the feedback path modeling adaptive filter operable to calculate feedback neutralization filter taps,

a first summing junction operable to subtract the first output signal from the modified modeling feedback signal to generate the feedback path modeling error signal which is provided to a first adaptive algorithm used by the feedback path modeling adaptive filter,

a secondary path signal discrimination circuitry operable to receive the error signal and to generate a modified modeling secondary path signal, the secondary path signal discrimination circuitry including;

a decorrelation delay unit operable to delay the error signal and to generate a delayed output signal that corresponds to a delayed error signal,

an adaptive discrimination filter operable to receive the delayed output signal and the modified modeling secondary path signal and to filter the delayed output signal to generate a predicted noise signal, and

a second summing junction operable to subtract the predicted noise signal from the error signal to generate the modified modeling secondary path signal,

a secondary path modeling adaptive filter operable to receive the modeling signal and a secondary path modeling error signal and to filter the modeling signal to generate a second output signal, the secondary path modeling adaptive filter operable to calculate secondary path compensation filter taps, and

a third summing junction operable to subtract the second output signal from the modified modeling secondary path signal to generate the secondary path modeling error signal which is provided to a second adaptive algorithm used by the secondary path modeling adaptive filter.

21. The off-line modeling system of claim 20, further comprising:

a first interface circuit operable to convert the primary signal in the analog domain to the digital domain and to provide the primary signal to the off-line modeling circuitry in the digital domain;

a second interface circuit operable to convert a secondary signal in the digital domain to the analog domain and to provide the secondary signal to the secondary source in the analog domain; and

a third interface circuit operable to convert the residual signal in the analog domain to the digital domain to generate the error signal in response, the third interface circuit operable to provide the error signal to the off-line modeling circuitry in the digital domain.

22. The off-line modeling system of claim 20, wherein the off-line modeling circuitry uses digital circuitry.

23. The off-line modeling system of claim 20, wherein the reference sensor is a microphone, and the secondary source is a speaker.

24. The off-line modeling system of claim 20, wherein the calculated feedback neutralization filter taps and the calculated secondary path compensation filter taps are stored in computer memory after being calculated.

25. An off-line modeling circuitry for modeling the feedback path and the secondary path of an active noise control system, the off-line modeling circuitry comprising:

a modeling signal generator operable to generate the modeling signal;

a feedback path signal discrimination circuitry operable to receive a primary signal and to generate a modified modeling feedback signal;

a feedback path modeling adaptive filter operable to receive the modeling signal and a feedback path modeling error signal and to filter the modeling signal to generate a first output signal, the feedback path modeling adaptive filter operable to calculate feedback neutralization filter taps;

a first summing junction operable to subtract the first output signal from the modified modeling feedback signal to generate the feedback path modeling error signal which is provided to a first adaptive algorithm used by the feedback path modeling adaptive filter;

a secondary path signal discrimination circuitry operable to receive an error signal and to generate a modified modeling secondary path signal, the secondary path signal discrimination circuitry including;

a decorrelation delay unit operable to delay the error signal and to generate a delayed output signal that corresponds to a delayed error signal,

an adaptive discrimination filter operable to receive the delayed output signal and the modified modeling secondary path signal and to filter the delayed output signal to generate a predicted noise signal, and

a second summing junction operable to subtract the predicted noise signal from the error signal to generate the modified modeling secondary path signal;

a secondary path modeling adaptive filter operable to receive the modeling signal and a secondary path modeling error signal and to filter the modeling signal to generate a second output signal, the secondary path modeling adaptive filter operable to calculate secondary path compensation filter taps; and

a third summing junction operable to subtract the second output signal from the modified modeling secondary path signal to generate the secondary path modeling error signal which is provided to filter the modeling signal to generate a first output signal, the feedback path modeling adaptive filter operable to calculate feedback neutralization filter taps;

a first summing junction operable to subtract the first output signal from the modified modeling feedback signal to generate the feedback path modeling error signal which is provided to a first adaptive algorithm used by the feedback path modeling adaptive filter;

a secondary path signal discrimination circuitry operable to receive an error signal and to generate a modified modeling secondary path signal, the secondary path signal discrimination circuitry including;

a decorrelation delay unit operable to delay the error signal and to generate a delayed output signal that corresponds to a delayed error signal,

an adaptive discrimination filter operable to receive the delayed output signal and the modified modeling secondary path signal and to filter the delayed output signal to generate a predicted noise signal, and

a second summing junction operable to subtract the predicted noise signal from the error signal to generate the modified modeling secondary path signal;

a secondary path modeling adaptive filter operable to receive the modeling signal and a secondary path modeling error signal and to filter the modeling signal to generate a second output signal, the secondary path modeling adaptive filter operable to calculate secondary path compensation filter taps; and

a third summing junction operable to subtract the second output signal from the modified modeling secondary path signal to generate the secondary path modeling error signal which is provided to a second adaptive algorithm used by the secondary path modeling adaptive filter.

26. The off-line modeling circuitry of claim 25, further comprising a memory for storing the feedback neutralization filter taps and the secondary path compensation filter taps.

27. The off-line modeling circuitry of claim 25, wherein the first adaptive algorithm used by the feedback path modeling adaptive filter is operable to calculate the feedback neutralization filter taps by minimizing the mean-square value of the feedback path modeling error signal, and wherein the second adaptive algorithm used by the secondary path modeling adaptive filter is operable to calculate the secondary path compensation filter taps by minimizing the mean-square value of the secondary path modeling error signal.

28. The off-line modeling circuitry of claim 25, wherein the delay of the decorrelation delay unit is a programmable delay.

29. The off-line modeling circuitry of claim 25, wherein the delay is equal to or greater than the delay of the secondary path being modeled.

30. The off-line modeling circuitry of claim 25, wherein the modeling signal generator is a white noise generator.

31. The off-line modeling circuitry of claim 25, wherein the error signal provided to the secondary path signal discrimination circuitry is provided from an error sensor.