Patent ID: 8150055

Claim:
An active noise control system comprising: an adaptive filter for being supplied with a reference signal that is correlated to first noise generated by a noise source on a vehicle, and generating a control signal based on the reference signal; noise output means for outputting third noise based on said control signal in order to cancel out second noise generated in the vehicle based on said first noise; noise detecting means for generating an error signal based on canceling error noise between said second noise and said third noise; reference signal correcting means for correcting said reference signal based on sound transfer characteristics from said noise output means to said noise detecting means, and outputting the corrected reference signal as a corrective signal; and filter coefficient updating means, having an imaginary term estimator for estimating an imaginary term of said error signal based on the error signal which comprises a real term, for updating a filter coefficient of said adaptive filter in order to minimize said error signal, based on said imaginary term estimated by said imaginary term estimator, said real term, and said corrective signal, wherein said imaginary term estimator has a real term differentiator for calculating a time differential value of said real term, and estimates said imaginary term based on the time differential value calculated by said real term differentiator.