Active noise control system and method for on-line feedback path modeling and on-line secondary path modeling

• US 5,940,519 A
• Filed: 12/17/1997
• Issued: 08/17/1999
• 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:
  US08/992,823
• Time in Patent Office: 608 Days
• Field of Search: 381/71.11, 381/71.12, 381/71.8, 381/71.5, 381/71.4, 381/71.3, 381/71.1, 364/724.19, 364/724.2
• 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 11/17879 using both a reference signal and an error signal
• 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

Abstract

A feedforward active noise control system (50) is provided that includes a reference sensor (16), a secondary source (18), an error sensor (20), and an active noise control system controller (10) for generating an anti-noise signal to attenuate a noise signal provided through a media. The feedforward active noise control system (50) performs on-line feedback path modeling and on-line secondary path modeling.

Claims

1. An active noise control system for generating an anti-noise signal to attenuate a noise signal provided through a media, the active noise control system performing on-line feedback path modeling and on-line secondary path modeling, the active noise control system comprising:

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

a secondary source operable to receive a secondary signal and to generate a corresponding anti-noise signal that is provided to the media to attenuate the noise signal;

an error sensor operable to receive a residual signal that is the combination of the noise signal and the anti-noise signal as received at the error sensor, and to generate an error signal in response; and

an active noise control system controller operable to receive the primary signal and the error signal and to generate the secondary signal while performing on-line feedback path modeling and on-line secondary path modeling, the active noise control system controller including;

a modeling signal generator operable to generate a modeling signal,

an on-line 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 on-line feedback path modeling adaptive filter operable to generate filter taps to minimize the feedback path modeling error signal,

a feedback signal discrimination circuitry operable to receive a feedback neutralized primary signal and to generate a modified modeling feedback signal,

a first summing junction operable to subtract the first output signal of the on-line feedback path modeling adaptive filter from the modified modeling feedback signal to generate the feedback path modeling error signal used by the on-line feedback path modeling adaptive filter,

a feedback neutralization filter operable to receive and use the filter taps generated by the on-line feedback path modeling adaptive filter and to filter a generated secondary signal to generate an anti-noise feedback component of the primary signal,

a second summing junction operable to subtract the anti-noise feedback component from the primary signal to generate the feedback neutralized primary signal,

an on-line 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 on-line secondary path modeling adaptive filter operable to generate filter taps to minimize the secondary path modeling error signal,

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

a third summing signal junction operable to subtract the second output signal of the on-line secondary path modeling adaptive filter from the modified modeling secondary path signal to generate the secondary path modeling error signal used by the on-line secondary path modeling adaptive filter,

a secondary path compensation filter operable to receive and use the filter taps generated by the on-line secondary path modeling adaptive filter and to filter the feedback neutralized primary signal to generate a secondary path compensated primary signal,

a system adaptive filter operable to receive the feedback neutralized primary signal, the error signal, and the secondary path compensated primary signal and to filter the feedback neutralized primary signal to generate a generated secondary signal, and

a fourth summing junction operable to combine the generated secondary signal with the modeling signal to generate the secondary signal.

2. The active noise control system of claim 1, further comprising:

a first interface circuit operable to convert the primary signal from the analog domain to the digital domain and to provide the primary signal to the active noise control system controller in the digital domain;

a second interface circuit operable to convert the secondary signal from 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 error signal from the analog domain to the digital domain and to provide the error signal to the active noise control system controller in the digital domain.

3. The active noise control system of claim 1, wherein the primary signal includes a noise signal component, an anti-noise feedback component and a modified modeling feedback component, and the error signal includes a modified modeling secondary path component.

4. The active noise control system of claim 1, wherein the average amplitude of the modeling signal is smaller than the average amplitude of the noise signal.

5. The active noise control system of claim 1, wherein the active noise control system is a feedforward active noise control system.

6. The active noise control system of claim 1, further comprising:

a fifth summing junction operable to subtract the modified modeling feedback signal from the feedback neutralized primary signal to generate a processed primary signal, and wherein the system adaptive filter is operable to receive the processed primary signal, the error signal, and the secondary path compensated primary signal and to filter the processed primary signal to generate the generated secondary signal.

7. An active noise control system controller for receiving a primary signal and an error signal and generating a secondary signal in response, the active noise control system controller comprising:

a modeling signal generator operable to generate a modeling signal;

an on-line 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 on-line feedback path modeling adaptive filter operable to generate filter taps to minimize the feedback path modeling error signal;

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

a first summing junction operable to subtract the first output signal of the on-line feedback path modeling adaptive filter from the modified modeling feedback signal to generate the feedback path modeling error signal used by the on-line feedback path modeling adaptive filter;

a feedback neutralization filter operable to receive and use the filter taps generated by the on-line feedback path modeling adaptive filter and to filter a generated secondary signal to generate an anti-noise feedback component of the primary signal;

a second summing junction operable to subtract the anti-noise feedback component from the primary signal to generate feedback neutralized primary signal;

an on-line 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 on-line secondary path modeling adaptive filter operable to generate filter taps to minimize the secondary path modeling error signal;

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

a third summing junction operable to subtract the second output signal of the on-line secondary path modeling adaptive filter from the modified modeling secondary path signal to generate the secondary path modeling error signal used by the on-line secondary path modeling adaptive filter;

a secondary path compensation filter operable to receive and use the filter taps generated by the on-line secondary path modeling adaptive filter and to filter the feedback neutralized primary signal to generate a secondary path compensated primary signal;

a system adaptive filter operable to receive the feedback neutralized primary signal, the error signal, and the secondary path compensated primary signal and to filter the feedback neutralized primary signal to generate a generated secondary signal; and

a fourth summing junction operable to combine the generated secondary signal with the modeling signal to generate the secondary signal.

8. The active noise control system controller of claim 7, further comprising:

a fifth summing junction operable to subtract the modified modeling feedback signal from the feedback neutralized primary signal to generate a processed primary signal, and wherein the system adaptive filter is operable to receive the processed primary signal, the error signal, and the secondary path compensated primary signal and to filter the processed primary signal to generate the generated secondary signal.

9. The active noise control system controller of claim 7, wherein the on-line feedback path modeling adaptive filter uses an adaptive algorithm to calculate the filter taps of the on-line feedback path modeling adaptive filter to minimize the mean-square value of the feedback path modeling error signal.

10. The active noise control system controller of claim 7, wherein the filter taps are provided to the feedback neutralization filter at desired intervals.

11. The active noise control system controller of claim 7, wherein the filter taps are provided to the secondary path compensation filter at desired intervals.

12. The active noise control system controller of claim 7, wherein the feedback signal discrimination circuitry includes:

a decorrelation delay unit operable to delay the feedback neutralized primary signal and to provide a delayed feedback neutralized primary signal;

an adaptive discrimination filter operable to receive the delayed feedback neutralized primary signal and the modified modeling feedback signal and to filter the delayed feedback neutralized primary signal to generate a predicted noise signal; and

a fifth summing junction operable to subtract the predicted noise signal from the feedback neutralized primary signal to generate the modified modeling feedback signal.

13. The active noise control system controller of claim 12, wherein the decorrelation delay unit is implemented using digital circuitry.

14. The active noise control system controller of claim 13, wherein the delay of the decorrelation delay unit is a programmable delay.

15. The active noise control system controller of claim 13, wherein the delay of the decorrelation delay unit is equal to or greater than the delay of the feedback path being modeled.

16. The active noise control system controller of claim 7, wherein the modeling signal generator is a white noise generator.

17. The active noise control system controller of claim 7, wherein the system adaptive filter includes an adaptive algorithm that uses a least-means-square adaptive algorithm.

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

receiving a primary signal;

generating a modeling signal;

s generating filter taps for use in a feedback neutralization filter using the modeling signal and a modified modeling feedback signal,

generating a feedback neutralized primary signal using the feedback neutralization filter;

generating the modified modeling feedback signal using the feedback neutralized primary signal;

receiving an error signal;

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

generating filter taps for use in a secondary path compensation filter using the modeling signal and the modified modeling secondary path signal;

generating a secondary path compensated primary signal using the secondary path compensation filter;

generating a generated secondary signal using the secondary path compensated primary signal and the feedback neutralized primary signal; and

generating a secondary signal using the generated secondary signal and the modeling signal.

19. The method of claim 18, wherein the generating the modified modeling feedback signal step includes using a digital delay that is equal to or greater than the delay of the feedback path being modeled.