A subtractor subtracts a first control signal output from a first bandpass filter from an error signal, and supplies a differential signal to a second bandpass filter. The second bandpass filter, which has a central frequency of 70 Hz, is affected by an operation of the first bandpass filter, i.e., a...http://www.google.com/patents/US20090067638?utm_source=gb-gplus-sharePatent US20090067638 - VEHICULAR ACTIVE VIBRATORY NOISE CONTROL APPARATUS
