Patent ID: 7792312
Filing Date: 2010-09-07
Classification: G10K,G10L

Abstract:
1. An active noise control system comprising: a base signal generator for outputting a harmonic base signal from the frequency of noise generated by a noise source; an adaptive notch filter for being supplied with said base signal and outputting a control signal for canceling out said noise; a sound output unit for outputting a control sound represented by said control signal; a sound detector for detecting a canceling error sound representing the difference between said noise and said control sound and outputting an error signal; a correcting filter having a transfer function from said sound output unit to said sound detector, for being supplied with said base signal and outputting a reference signal; first filter coefficient updating means for being supplied with said error signal and said reference signal and successively updating a filter coefficient of said adaptive notch filter in order to minimize said error signal; second filter coefficient updating means for updating said filter coefficient by multiplying the filter coefficient to be updated of said adaptive notch filter by a predetermined value smaller than 1; and switching means for alternatively switching between said first filter coefficient updating means and said second filter coefficient updating means and supplying said filter coefficient to said adaptive notch filter; wherein said switching means switches to a filter coefficient supplied from said second filter coefficient updating means when said filter coefficient is equal to or greater than a first threshold value and switches to a filter coefficient supplied from said first filter coefficient updating means when said filter coefficient is smaller than a second threshold value which is smaller than said first threshold value.