Patent ID: 9646596
Date: 2017-05-09
CPC Classifications: G10K

Claim:
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.