Active noise control system

An active noise control system comprising:

• a cosine-wave generator for generating a cosine-wave signal in synchronization with a frequency of a problematic cyclic noise generated at a noise source;
• a sine-wave generator for generating a sine-wave signal in synchronization with the frequency of said problematic noise;
• a first one-tap adaptive filter for receiving a reference cosine-wave signal outputted from said cosine-wave generator;
• a second one-tap adaptive filter for receiving a reference sine-wave signal outputted from said sine-wave generator;
• an adder for adding together an output signal from said first one-tap adaptive filter and an output signal from said second one-tap adaptive filter;
• secondary noise generator means, driven by an output signal from the adder, for producing a secondary noise to cancel said problematic noise;
• residual signal detection means for sensing a residual signal resulting from interference between said secondary noise and said problematic noise;
• simulation signal generator means for receiving said reference cosine-wave signal and said reference sine-wave signal to generate a simulation cosine-wave signal and a simulation sine-wave signal, said simulation cosine-wave and sine-wave signals being compensated in accordance with characteristics simulating transfer characteristics between said secondary noise generator means and said residual signal detection means;
• and
• compensated signal generator means for generating a compensated signal obtained by compensating the same signal as the output signal from said adder in accordance with the characteristics simulating the transfer characteristics between said secondary noise generator means and said residual signal detection means, wherein
• the output signal from said residual signal detection means, the output signal from said simulation signal generator means, and the output signal from said compensated signal generator means are used to update filter coefficients of said first one-tap adaptive filter and said second one-tap adaptive filter, thereby reducing said problematic noise at said residual signal detection means.