Active noise-reduction control apparatus and method

• US 20070076896A1
• Filed: 08/07/2006
• Published: 04/05/2007
• Est. Priority Date: 09/28/2005
• Status: Abandoned Application

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Hosaka, Rika, Enamito, Akihiko, Kojima, Kenji, Kijimoto, Shinya
• Application Number:
  US11/501,332
• Publication Number:
  US 20070076896A1
• Time in Patent Office: Days
• US Class Current: 381/71.110
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17835 using detection of abnormal input signals
• 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 2210/3028 Filtering, e.g. Kalman filters or special analogue or digital filters

Abstract

Apparatus includes generator generating reference signal based on noise emitted from sound source, detector detecting level of reference signal and change in level, unit comparing change with threshold-value range and produce compared result, filter filtering reference signal, adaptive filter having variable filter coefficient, unit updating filter coefficient according to change of level of reference signal for obtaining an updated filter coefficient, unit stopping updating of filter coefficient in response to compared result when change falls outside threshold-value range, unit storing updated filter coefficient each time filter coefficient is updated, generator generating control signal using stored filter coefficient, unit generating control sound based on control signal, microphone detecting synthesis sound pressure of control sound and noise to produce an error signal, and unit setting stored filter coefficient to more accurate coefficient than stored filter coefficient based on error signal, and signal acquired by filtering control signal through filter.

Claims

1. An active noise-reduction control apparatus comprising:

a reference signal generator which generates a reference signal based on noise emitted from a sound source;

a detector which detects a level of the reference signal and a change in the level;

a comparison unit configured to compare the change with a threshold-value range and produce a compared result;

an adaptive filter configured to filter the reference signal, the adaptive filter having a variable filter coefficient;

an updating unit configured to update the filter coefficient according to the change of the level of the reference signal for obtaining an updated filter coefficient;

a stop unit configured to stop updating of the filter coefficient in response to the compared result when the change falls outside the threshold-value range;

a storage unit configured to store the updated filter coefficient each time the filter coefficient is updated;

a control signal generator which generates a control signal using the stored filter coefficient;

a control-sound source unit configured to generate a control sound based on the control signal;

an error microphone which detects synthesis sound pressure of the control sound and the noise to produce an error signal; and

a setting unit configured to set the stored filter coefficient to a more accurate coefficient than the stored filter coefficient based on the error signal, and a signal acquired by filtering the control signal through the adaptive filter.

2. The apparatus according to claim 1, wherein the setting unit is configured to set the stored filter coefficient using a least mean square (LMS) algorithm.

3. The apparatus according to claim 1, wherein the setting unit is configured to set the stored filter coefficient using a fast transversal filter (FTF) algorithm.

4. An active noise-reduction control apparatus comprising:

a reference signal generator which generates a reference signal based on noise emitted from a sound source;

a detector which detects a level of the reference signal and a change in the level;

a comparison unit configured to compare the change with a threshold-value range and produce a compared result;

an adaptive filter configured to filter the reference signal, the adaptive filter having a variable filter coefficient;

an initialization unit configured to initialize the filter coefficient in response to the compared result when the change falls outside the threshold-value range;

a control signal generator which generates a control signal using the filter coefficient;

a control-sound source unit configured to generate a control sound based on the control signal;

an error microphone which detects synthesis sound pressure of the control sound and the noise to produce an error signal; and

a setting unit configured to set the filter coefficient to a more accurate coefficient than the filter coefficient based on the error signal, and a signal acquired by filtering the control signal through the adaptive filter.

5. The apparatus according to claim 4, wherein the setting unit is configured to set the filter coefficient using a least mean square (LMS) algorithm.

6. The apparatus according to claim 4, wherein the setting unit is configured to set the filter coefficient using a fast transversal filter (FTF) algorithm.

7. An active noise-reduction control apparatus comprising:

a reference signal generator which generates a reference signal based on noise emitted from a sound source;

a control-sound source unit configured to generate a control sound used for controlling reduction of the noise;

an error microphone which detects synthesis sound pressure of the control sound and the noise to produce an error signal;

a computation unit configured to compute an estimated error based on the reference signal and the error signal;

an adaptive filter configured to filter the reference signal, the adaptive filter having a variable filter coefficient;

an adjustment unit configured to adjust the filter coefficient based on the estimated error;

a control signal generator which generates a control signal using the filter coefficient; and

a setting unit configured to set the filter coefficient to a more accurate coefficient than the filter coefficient based on the error signal, and a signal acquired by filtering the control signal through the adaptive filter,

the control-sound source unit generating the control sound based on the control signal.

8. The apparatus according to claim 7, wherein the setting unit is configured to set the filter coefficient using a least mean square (LMS) algorithm.

9. The apparatus according to claim 7, wherein the setting unit is configured to set the filter coefficient using a fast transversal filter (FTF) algorithm.

10. An active noise-reduction control apparatus comprising:

a reference signal generator which generates a reference signal based on noise emitted from a sound source;

a detector which detects a level of the reference signal and a change in the level;

a comparison unit configured to compare the change with a threshold-value range and produce a compared result;

a first adaptive filter configured to filter the reference signal, the first adaptive filter having a first variable filter coefficient;

a first updating unit configured to update the first variable filter coefficient according to the change of the level of the reference signal for obtaining an updated first variable filter coefficient;

a first stop unit configured to stop updating of the first variable filter coefficient in response to the compared result when the change falls outside the threshold-value range;

a first control signal generator which generates a first control signal using the first variable filter coefficient;

a first control-sound source unit configured to generate a first control sound based on the first control signal;

a first error microphone which detects first synthesis sound pressure of the first control sound and the noise to produce a first error signal;

a first setting unit configured to set the first variable filter coefficient to a more accurate coefficient than the first variable filter coefficient based on the first error signal, and a signal acquired by filtering the first control signal through the first adaptive filter;

a second adaptive filter configured to filter the reference signal, the second adaptive filter having a second variable filter coefficient;

a second updating unit configured to update the second variable filter coefficient according to the change of the level of the reference signal for obtaining an updated second variable filter coefficient;

a second stop unit configured to stop updating of the second variable filter coefficient in response to the compared result when the change falls outside the threshold-value range;

a second control signal generator which generates a second control signal using the second variable filter coefficient;

a second control-sound source unit configured to generate a second control sound based on the second control signal;

a second error microphone which detects second synthesis sound pressure of the second control sound and the noise to produce a second error signal;

a second setting unit configured to set the second variable filter coefficient to a more accurate coefficient than the second variable filter coefficient based on the second error signal, and a signal acquired by filtering the second control signal through the second adaptive filter.

11. The apparatus according to claim 10, wherein the first setting unit and the second setting unit are configured to set the filter coefficient a least mean square (LMS) algorithm.

12. The apparatus according to claim 10, wherein the first setting unit and the second setting unit are configured to set the filter coefficient using a fast transversal filter (FTF) algorithm.

13. An active noise-reduction control method comprising:

generating a reference signal based on noise emitted from a sound source;

detecting a level of the reference signal and a change in the level;

comparing the change with a threshold-value range and producing a compared result;

preparing an adaptive filter configured to filter the reference signal, the adaptive filter having a variable filter coefficient;

updating the filter coefficient according to the change of the level of the reference signal for obtaining an updated filter coefficient;

stopping updating of the filter coefficient in response to the compared result when the change falls outside the certain threshold-value range;

preparing a storage unit configured to store the updated filter coefficient each time the filter coefficient is updated;

generating a control signal using the stored filter coefficient;

generating a control sound based on the control signal;

detecting synthesis sound pressure of the control sound and the noise to produce an error signal; and

setting the stored filter coefficient to a more accurate coefficient than the stored filter coefficient based on the error signal, and a signal acquired by filtering the control signal through the adaptive filter.

14. An active noise-reduction control method comprising:

generating a reference signal based on noise emitted from a sound source;

detecting a level of the reference signal and a change in the level;

comparing the change with a threshold-value range and producing a compared result;

preparing an adaptive filter configured to filter the reference signal, the adaptive filter having a variable filter coefficient;

initializing the filter coefficient in response to the compared result when the change falls outside the threshold-value range;

generating a control signal using the filter coefficient;

generating a control sound based on the control signal;

detecting synthesis sound pressure of the control sound and the noise to produce an error signal; and

setting the filter coefficient to a more accurate coefficient than the filter coefficient based on the error signal, and a signal acquired by filtering the control signal through the adaptive filter.

15. An active noise-reduction control method comprising:

generating a reference signal based on noise emitted from a sound source;

generating a control sound used for controlling reduction of the noise;

detecting synthesis sound pressure of the control sound and the noise and producing an error signal;

computing an estimated error based on the reference signal and the error signal;

preparing an adaptive filter configured to filter the reference signal, the adaptive filter having a variable filter coefficient;

adjusting the filter coefficient based on the estimated error;

generating a control signal using the filter coefficient; and

setting the filter coefficient to a more accurate coefficient than the filter coefficient based on the error signal, and a signal acquired by filtering the control signal through the adaptive filter,

generating the control sound based on the control signal.

16. An active noise-reduction control method comprising:

generating a reference signal based on the noise emitted from a sound source;

detecting a level of the reference signal and a change in the level;

comparing the change with a threshold-value range and producing a compared result;

preparing a first adaptive filter configured to filter the reference signal, the first adaptive filter having a first variable filter coefficient;

updating the first variable filter coefficient according to the change of the level of the reference signal for obtaining an updated first variable filter coefficient;

stopping updating of the first variable filter coefficient in response to the compared result when the change falls outside the threshold-value range;

generating a first control signal using the first variable filter coefficient;

generating a first control sound based on the first control signal;

detecting first synthesis sound pressure of the first control sound and the noise and producing a first error signal;

setting the first variable filter coefficient to a more accurate coefficient than the first variable filter coefficient based on the first error signal, and a signal acquired by filtering the first control signal through the first adaptive filter;

preparing a second adaptive filter configured to filter the reference signal, the second adaptive filter having a second variable filter coefficient;

updating the second variable filter coefficient according to the change of the level of the reference signal for obtaining an updated second variable filter coefficient;

stopping updating of the second variable filter coefficient in response to the compared result when the change falls outside the threshold-value range;

generating a second control signal using the second variable filter coefficient;

generating a second control sound based on the second control signal;

detecting second synthesis sound pressure of the second control sound and the noise to produce a second error signal;

setting the second variable filter coefficient to a more accurate coefficient than the second variable filter coefficient based on the second error signal, and a signal acquired by filtering the second control signal through the second adaptive filter.