In active noise control (ANC), there are two problems that lead to a poor control performance. At first, if the acoustic transfer characteristic from control loudspeakers to error microphone has notch characteristic, the effectiveness of ANC decreases on this frequency. Second if the acoustic transfer characteristic has notch or resonance characteristic, adaptive speed has to set slowly. So it decreases the convergence speed. To solve these problems, we propose a new ANC method not depending on the acoustic transfer characteristic. Specifically, two control loudspeakers and two digital filters are used to make acoustic transfer characteristic flat within control frequency. Moreover we extend this new method to sound reduction of repeated impulsive sound. We also indicate the result of experiment to demonstrate the effectiveness of new ANC method and extended new ANC method.
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