| 摘要 |
PURPOSE: To decrease the number of arithmetic processors irrelevantly to the number of noise sources as to a method which reduces synchronous noises by a sound eliminating method using a synchronous adaptive filter. CONSTITUTION: A sampling frequency which is constant irrelevantly to a noise frequency is used and then even if the frequency of a noise varies, propagation characteristic data from a secondary sound source 3 to a monitor microphone 2 which are acquired before control can be used consistently. Further, a start point of time of each cycle of the noise is determined on the basis of an oversampling timeΔT' as a constant interval which is set more finely than a sampling timeΔT for the input and output of an actual signal, so the deviation in time between the noise waveform and control waveform becomes less than the extremely short oversampling time and the control is possible without using resetting.
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