Active noise-reduction apparatus and method

Patent metadata

Field	Value
Publication number	US-9318093-B2
Application number	US-201414495068-A
Country	US
Kind code	B2
Filing date	Sep 24, 2014
Priority date	Sep 24, 2013
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

According to an embodiment, an active noise-reduction apparatus includes following elements. The microphone converts a sound including a target sound into an error signal. The control filter generates a control signal in accordance with a control characteristic. The first control effect estimation filter converts the control signal into a first signal in accordance with an estimated secondary path characteristic. The second control effect estimation filter converts the control signal into a second signal in accordance with a processed secondary path characteristic obtained by shortening a delay of the estimated secondary path characteristic. The updating unit updates the control characteristic based on the error signal, the first signal, and the second signal.

First claim

What is claimed is:

1. An active noise-reduction apparatus for reducing a target sound having periodicity, the apparatus comprising:
an error microphone which converts a sound including the target sound into a first error signal;
a reference signal generator configured to generate a reference signal;
a control filter configured to convert, in accordance with a control characteristic, the reference signal into a control signal used to cancel the target sound;
a control loudspeaker which emits a control sound based on the control signal;
a first control effect estimation filter configured to convert the control signal into a first signal in accordance with an estimated secondary path characteristic, the estimated secondary path characteristic being generated based on a result of identifying a secondary path characteristic from the control loudspeaker to the error microphone in advance;
an estimated noise signal generator configured to generate an estimated noise signal by subtracting the first signal from the first error signal;
a second control effect estimation filter configured to convert the control signal into a second signal in accordance with a processed secondary path characteristic, the processed secondary path characteristic being obtained by shortening a delay included in the estimated secondary path characteristic by a time, the time corresponding to a period of the target sound multiplied by a constant; and
an updating unit configured to update the control characteristic so that a second error signal which is a sum of the estimated noise signal and the second signal is minimized,
wherein letting T be the period, a be the delay, and m be the constant, the constant is a positive integer satisfying T×m≦a.

2. The apparatus according to claim 1 , wherein the constant is a maximum integer satisfying T×m≦a.

3. The apparatus according to claim 1 , wherein the reference signal generator comprises a reference microphone which converts the target sound into the reference signal.

4. The apparatus according to claim 1 , wherein the reference signal generator comprises the estimated noise signal generator, and the reference signal is the estimated noise signal.

5. The apparatus according to claim 1 , further comprising:
a period calculation unit configured to calculate the period based on the reference signal; and
a determination unit configured to determine the processed secondary path characteristic based on the calculated period.

6. An active noise-reduction apparatus for reducing a target sound, the apparatus comprising:
an error microphone which converts a sound including the target sound into an error signal;
a reference signal generator configured to generate a reference signal;
a control filter configured to convert, in accordance with a control characteristic, the reference signal into a control signal used to cancel the target sound;
a control loudspeaker which emits a control sound based on the control signal;
a control effect estimation filter configured to convert the control signal into a first signal in accordance with an estimated secondary path characteristic, the estimated secondary path characteristic generated based on a result of identifying a secondary path characteristic from the control loudspeaker to the error microphone in advance;
a secondary path filter configured to convert the reference signal into a first auxiliary signal in accordance with the estimated secondary path characteristic;
a virtual control effect estimation filter configured to convert the first auxiliary signal into a second signal in accordance with the control characteristic; and
an updating unit configured to update the control characteristic so that an evaluation function based on the error signal and a second auxiliary signal is minimized, the second auxiliary signal being a difference between the second signal and the first signal.

7. The apparatus according to claim 6 , wherein the reference signal generator comprises a reference microphone which converts the target sound into the reference signal.

8. The apparatus according to claim 6 , wherein the reference signal generator generates the reference signal by subtracting the first signal from the error signal.

9. An active noise-reduction method for reducing a target sound having periodicity, the method comprising:
providing an error microphone which converts a sound including the target sound into a first error signal;
generating a reference signal;
converting, in accordance with a control characteristic, the reference signal into a control signal used to cancel the target sound;
providing a control loudspeaker which emits a control sound based on the control signal;
converting the control signal into a first signal in accordance with an estimated secondary path characteristic, the estimated secondary path characteristic being generated based on a result of identifying a secondary path characteristic from the control loudspeaker to the error microphone in advance;
generating an estimated noise signal by subtracting the first signal from the first error signal;
converting the control signal into a second signal in accordance with a processed secondary path characteristic, the processed secondary path characteristic being obtained by shortening a delay included in the estimated secondary path characteristic by a time, the time corresponding to a period of the target sound multiplied by a constant; and
updating the control characteristic so that a second error signal which is a sum of the estimated noise signal and the second signal is minimized,
wherein letting T be the period, a be the delay, and m be the constant, the constant is a positive integer satisfying T×m≦a.

10. The method according to claim 9 , wherein the constant is a maximum integer satisfying T×m≦a.

11. The method according to claim 9 , wherein the generating the reference signal comprises providing a reference microphone which converts the target sound into the reference signal.

12. The method according to claim 9 , wherein the reference signal is the estimated noise signal.

13. The method according to claim 9 , further comprising:
calculating the period based on the reference signal; and
determining the processed secondary path characteristic based on the calculated period.

14. An active noise-reduction method for reducing a target sound, the method comprising:
providing an error microphone which converts a sound including the target sound into an error signal;
generating a reference signal;
converting, in accordance with a control characteristic, the reference signal into a control signal used to cancel the target sound;
providing a control loudspeaker which emits a control sound based on the control signal;
converting the control signal into a first signal in accordance with an estimated secondary path characteristic, the estimated secondary path characteristic generated based on a result of identifying a secondary path characteristic from the control loudspeaker to the error microphone in advance;
converting the reference signal into a first auxiliary signal in accordance with the estimated secondary path characteristic;
converting the first auxiliary signal into a second signal in accordance with the control characteristic; and
updating the control characteristic so that an evaluation function based on the error signal and a second auxiliary signal is minimized, the second auxiliary signal being a difference between the second signal and the first signal.

15. The method according to claim 14 , wherein the generating the reference signal comprises prov

Assignees

• Toshiba Kk

Inventors

• Goto Tatsuhiko

Classifications

• G10K2210/3055

  Transfer function of the acoustic system · CPC title

• G10K2210/3027

  Feedforward · CPC title

• G10K2210/3044

  Phase shift, e.g. complex envelope processing · CPC title

• G10K2210/3028

  Filtering, e.g. Kalman filters or special analogue or digital filters · CPC title

• G10K2210/3016

  Control strategies, e.g. energy minimization or intensity measurements · CPC title