| 摘要 |
PURPOSE:To provide a muffler capable of safely controlling noise by using active noise control and automatically stopping coefficient renewal of an adaptive filter before becoming noise addition. CONSTITUTION:This muffler is constituted of a microphone 1a detecting the noise, a speaker 7 set up on a position far from a noise source compared with the set-up position of time microphone 1a, the microphone 1b set up on the position far from the noise source in the vicinity of the speaker 7, the adaptive filter 2 adaptive controlling so that the noise in the microphone 1b is attenuated, an LMS ALU (least mean square arithmetic and logic unit) 4 operating and updating the coefficient of the adaptive filter 2, an averaging means 10 calculating the mean value of the error signal of the microphone 1b, a comparison means 11 comparing values at every unit time of the mean value of the error signal and a stoppage means 12 stopping the coefficient renewal of the adaptive filter 2 by the LMS ALU 4 at the point of time when the attenuation of the error signal is converged. |
