Active noise reduction device, instrument using same, and active noise reduction method

Patent metadata

Field	Value
Publication number	US-9646596-B2
Application number	US-201414762482-A
Country	US
Kind code	B2
Filing date	Jan 21, 2014
Priority date	Jan 28, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

In an active noise reduction device, in order to solve this problem, a control block determines a level of a reference signal detected by a level detection unit. If determining that the level of the reference signal is small, the control block decreases a level of a cancel signal. This operation suppresses generation of an abnormal sound even if a level of a noise is small.

First claim

The invention claimed is:

1. An active noise reduction device comprising:
a reference signal input terminal configured to have a reference signal input thereto, the reference signal having a correlation with a noise;
a cancel signal generation block including at least an adaptive filter, the cancel signal generation block configured to output a cancel signal in accordance with the reference signal;
an output terminal configured to output the cancel signal output from the cancel signal generation block;
an error signal input terminal configured to have an error signal input thereto, the error signal corresponding to a residual sound caused by interference between the noise and a cancel sound generated from a cancel sound source in response to the cancel signal;
a data filter configured to have the reference signal input thereto and to output a filtered reference signal obtained by correcting the reference signal with simulated acoustic transfer characteristic data that simulates an acoustic transfer characteristic of a signal transfer path of the cancel signal;
a least mean square operation unit configured to update a filter coefficient of the cancel signal generation block by using the error signal, the filtered reference signal, and a step size parameter;
a level detection unit configured to have the reference signal input thereto; and
a control block configured to have a signal level input thereto, the signal level being detected by the level detection unit to determine the signal level,
wherein the signal transfer path is a signal path from the cancel signal generation block to the least mean square operation unit, and
wherein the control block decreases a level of the cancel signal when the signal level of the reference signal is equal to or less than a predetermined value.

2. The active noise reduction device according to claim 1 , wherein the control block adjusts at least one of the cancel signal output from the cancel signal generation block, the reference signal input into the cancel signal generation block, and the filter coefficient of the adaptive filter.

3. The active noise reduction device according to claim 1 , wherein the control block generates a level adjustment coefficient in accordance with the signal level, and adjusts the level of the cancel signal in accordance with the level adjustment coefficient.

4. The active noise reduction device according to claim 3 , wherein the control block adjusts the level of the cancel signal by multiplying, by the level adjustment coefficient, at least one of the cancel signal output from the cancel signal generation block, the reference signal input to the cancel signal generation block, and the filter coefficient of the adaptive filter.

5. The active noise reduction device according to claim 4 , wherein the control block decreases a value of the level adjustment coefficient when the signal level of the reference signal is equal to or less than the predetermined value.

6. The active noise reduction device according to claim 1 , further comprising:
an adjustment unit configured to adjust the level of the cancel signal in accordance with an output of the control block,
wherein the control block decreases the level of the cancel signal via the adjustment unit.

7. The active noise reduction device according to claim 6 ,
wherein the control block generates a level adjustment coefficient in accordance with the signal level, and
wherein the adjustment unit multiplies, by the level adjustment coefficient, at least one of the cancel signal output from the cancel signal generation block, the reference signal input into the cancel signal generation block, and the filter coefficient of the adaptive filter.

8. The active noise reduction device according to claim 6 , wherein the cancel signal generation block includes the adjustment unit.

9. The active noise reduction device according to claim 6 , wherein the control block decreases a value of the level adjustment coefficient when the signal level of the reference signal is equal to or less than the predetermined value.

10. The active noise reduction device according to claim 6 ,
wherein the least mean square operation unit includes the adjustment unit or serves as the adjustment unit, and
wherein the adjustment unit adjusts the filter coefficient to be output to the cancel signal generation block in accordance with the output of the control block.

11. The active noise reduction device according to claim 6 ,
wherein the adjustment unit includes a switch,
wherein the switch is provided at least one of between the cancel signal generation block and the reference signal source, and between the cancel signal generation block and the cancel sound source, and
wherein the switch is turned off when it is determined that the signal level of the reference signal is equal to or less than a predetermined value.

12. The active noise reduction device according to claim 6 , further comprising
a filter that is one of a high pass filter and a band pass filter to which the reference signal is supplied,
wherein the adjustment unit is operable to:
invert a phase of a high-frequency component signal output from the filter, and
add the cancel signal to a signal generated by convoluting the high-frequency component signal that has the inverted phase with the filter coefficient.

13. The active noise reduction device according to claim 6 , further comprising
a filter that is one of a high pass filter and a band pass filter to which the reference signal is supplied,
wherein the adjustment unit is operable to:
invert a phase of a high-frequency component signal output from the filter; and
sum up the reference signal and the high-frequency component signal that has the inverted phase.

14. The active noise reduction device according to claim 1 , wherein, when it is determined that a level of the reference signal is equal to or less than the predetermined value, the control block adjusts at least one of the cancel signal, the reference signal, the filter coefficient, and the level adjustment coefficient to zero so as to stop outputting of the cancel signal.

15. An active noise reduction device comprising:
a reference signal input terminal configured to have a reference signal input thereto, the reference signal having a correlation with a noise;
a cancel signal generation block including at least an adaptive filter, the cancel signal generation block configured to output a cancel signal in accordance with the reference signal;
an output terminal configured to output the cancel signal output from the cancel signal generation block;
an error signal input terminal configured to have an error signal input thereto, the error signal corresponding to a residual sound caused by interference between the noise and a cancel sound generated from a cancel sound source in response to the cancel signal;
a data filter configured to have the reference signal input thereto and to output a filtered reference signal obtained by correcting the reference signal with simulated acoustic transfer characteristic data that simulates an acoustic transfer-characteristic of a signal transfer path of the cancel signal;
a least mean square operation unit configured to update a filter coefficient of the cancel signal generation block by using the error signal, the filtered reference signal, and a step size parameter;
a level detection unit configured to have the reference signal input thereto; and
a control block configured to have a signal level input thereto, the signal level being detected by the level detection unit to determine the signal

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Tani Mitsuhiro
• Kaitou Mitsuru
• Funayama Toshiyuki

Classifications

• G10K11/178

  by electro-acoustically regenerating the original acoustic waves in anti-phase · CPC title

• G10K11/175 Primary

  using interference effects; Masking sound · CPC title

• G10K2210/3039

  Nonlinear, e.g. clipping, numerical truncation, thresholding or variable input and output gain · CPC title

• G10K2210/3016

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

• G10K2210/1282

  Automobiles · CPC title