Active-noise-reduction device, and active-noise-reduction system, mobile device and active-noise-reduction method which use same

Patent metadata

Field	Value
Publication number	US-9445192-B2
Application number	US-201314401094-A
Country	US
Kind code	B2
Filing date	Jun 21, 2013
Priority date	Jun 28, 2012
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

A reference signal generating unit of an active-noise-reduction device of the present invention outputs a referencing signal having a correlation with a vibration to an adaptive filter unit. A filter coefficient update unit receives an input of an error signal, and successively updates a filter coefficient of the adaptive filter unit. The error signal is generated by a cancelling sound based on the output of the adaptive filter unit and noise. The detection unit detects a filter coefficient of the filter coefficient update unit, and determines a size of the output of the adaptive filter unit. Then, the amplitude of the cancelling sound is adjusted based on the size of the output of the adaptive filter unit estimated by the detection unit.

First claim

The invention claimed is:

1. An active-noise-reduction device, comprising:
a first input terminal for receiving, from outside, a signal having a correlation with noise;
a signal processing device configured to provide:
a reference signal generating unit configured to output a reference signal based on the signal having the correlation with noise;
an adaptive filter unit into which the reference signal is input and from which a cancelling signal is output; and
a correction unit into which the reference signal is input and configured to generate a correction reference signal based on simulated acoustic transfer characteristics data that simulate acoustic transfer characteristics of a signal transfer path of the cancelling signal;

an output terminal for supplying the cancelling signal to outside;
a second input terminal into which an error signal based on a residual sound by interference between the cancelling signal and the noise is input;
wherein the signal processing device is further configured to provide:
a filter coefficient update unit configured to sequentially update a filter coefficient of the adaptive filter unit based on the error signal and the correction reference signal; and
a detection unit configured to detect the filter coefficient,
wherein the detection unit generates a control signal for adjusting an amplitude of the cancelling signal based on the detected filter coefficient.

2. The active-noise-reduction device of claim 1 , wherein the detection unit estimates whether or not the filter coefficient is saturated when the amplitude of the cancelling signal is reduced, and
when the detection unit estimates that the filter coefficient is not saturated, the detection unit reduces the amplitude of the cancelling signal by the control signal.

3. The active-noise-reduction device of claim 1 , wherein when the detection unit determines that the filter coefficient is in a saturation state, the detection unit adjusts the amplitude of the cancelling signal such that the saturation state is eliminated by the control signal.

4. The active-noise-reduction device of claim 3 , wherein when the detection unit detects that the filter coefficient of the adaptive filter unit exceeds an upper threshold, the detection unit determines that the filter coefficient is in a saturation state and increases the amplitude of the cancelling signal by the control signal.

5. The active-noise-reduction device of claim 3 , wherein the detection unit monitors the filter coefficient for a predetermined time, for obtaining a plurality of filter coefficients, and determines whether or not the filter coefficient is in a saturation state based on the plurality of filter coefficients.

6. The active-noise-reduction device of claim 5 , wherein when the detection unit detects that a maximum value of the plurality of filter coefficients exceeds a predetermined upper threshold, the detection unit determines that the filter coefficient is in a saturation state and reduces the amplitude of the cancelling signal by the control signal.

7. The active-noise-reduction device of claim 5 , wherein when the detection unit detects that two or more consecutive filter coefficients in the plurality of filter coefficients exceed a predetermined upper threshold, the detection unit determines that the filter coefficient is in a saturation state.

8. The active-noise-reduction device of claim 5 , wherein when the detection unit detects that two or more consecutive filter coefficients in the plurality of filter coefficients exceed a predetermined upper threshold and detects that a newest filter coefficient in the plurality of filter coefficients is changed so as to be saturated with respect to a previous filter coefficient, the detection unit determines that the filter coefficient is in a saturation state, and reduces the amplitude of the cancelling signal by the control signal.

9. The active-noise-reduction device of claim 1 , wherein the detection unit monitors the filter coefficient for a predetermined time, for obtaining a plurality of filter coefficients, estimates whether or not the filter coefficient is saturated based on the plurality of filter coefficients when the amplitude of the cancelling signal is reduced, and reduces the amplitude of the cancelling signal by the control signal when the detection unit estimates that the filter coefficient is not saturated even if the amplitude of the cancelling signal is reduced.

10. The active-noise-reduction device of claim 1 , wherein when the detection unit monitors the filter coefficient for a predetermined time, for obtaining a plurality of filter coefficients and detects that a maximum value in the plurality of filter coefficients is a predetermined lower threshold or less, the detection unit reduces the amplitude of the cancelling signal by the control signal.

11. The active-noise-reduction device of claim 1 , further comprising an amplitude adjustment unit between the adaptive filter unit and the output terminal,
wherein the detection unit supplies the amplitude adjustment unit with the control signal, and the amplitude adjustment unit adjusts the amplitude of the cancelling signal based on the control signal.

12. The active-noise-reduction device of claim 1 , wherein the detection unit adjusts a step-size parameter of the filter coefficient update unit based on a value of the control signal, and supplies the filter coefficient update unit with the adjusted step-size parameter.

13. The active-noise-reduction device of claim 1 , wherein an output from the detection unit is supplied to the correction unit or the reference signal generating unit, and the filter coefficient update unit updates the filter coefficient based on a correction reference signal corrected in response to the output from the detection unit.

14. The active-noise-reduction device of claim 1 , further comprising an amplitude adjustment unit between the adaptive filter unit and the output terminal,
wherein the amplitude adjustment unit is supplied with the control signal, and adjusts the amplitude of the cancelling signal.

15. An active-noise-reduction system comprising:
an active-noise-reduction device as defined in claim 1 ; and
a referencing signal source configured to generate a referencing signal to be supplied to the active-noise-reduction device, the referencing signal having a correlation with noise;
a transducer device configured to provide a cancelling sound source for generating a cancelling sound based on a cancelling signal output from the active-noise-reduction device;
an amplitude adjustment unit provided between the cancelling sound source and an adaptive filter unit of the active-noise-reduction device; and
an error signal detection circuit configured to generate an error signal based on a residual sound by interference between the cancelling sound and the noise, and outputting the error signal to the active-noise-reduction device;
wherein the amplitude adjustment unit is supplied with a control signal output from the detection unit of the active-noise-reduction device, and controls an amplitude of the cancelling signal based on the control signal.

16. A mobile device comprising:
a device main body;
a drive unit and an active-noise-reduction system mounted on the device main body; and
a space provided in the device main body,
wherein the active-noise-reduction system comprises:
an active-noise-reduction device as defined in claim 1 ; and
a referencing signal source configured to generate a referencing signal to be supplied to the active-noise-reduction device, the referencing signal

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Ueno Shotaro
• Nakamura Yoshio

Classifications

• H04R3/002 Primary

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