MUFFLER DEVICE

PURPOSE:To muffle a noise entering a duct ranging from a higher tone band to a lower tone band. CONSTITUTION:This device is constituted of a senser microphone 3 outputting a noise signal, an additional sound source speaker 2 radiating an additional sound, an error microphone 8 outputting a residual noise signal and a signal processing part 7 provided with a controlled filter 13 capable of controlling a filter coefficient and an adaptive filter 12. The signal processing part 7 performs adaptive control by the adaptive filter 12 so as to minimize a residual noise, and the calculated filter coefficient is supplied to the controlled filter 13. The controlled filter 13 performs convolutional operation for the inputted noise signal by the supplied filter coefficient to supply to the additional sound source speaker 2 as the additional sound signal. The number of taps of the adaptive filter 12 is divided to optional blocks, and the signal processing part 7 selects the block of the adaptive filter 12 successively at every one sampling period, and updates the coefficient in the selected block.