| 摘要 |
PURPOSE:To make it possible to execute adaptive control definitely by detecting fluctuations in transfer characteristics of an air supply duct during the execution of an active silencing control and correcting the setting of a digital filter. CONSTITUTION:A sound source microphone 22, a speaker 23 and an evaluation microphone 24 are installed in an air supply duct 21. An FIR filter 26 forces the speaker 23 to output an interference sound based on a detected sound from the sound source microphone 22, thereby executing active silencing control. An arithmetic operation factor of the FIR filter 26 is properly changed and set by means of an adaptive filter 32 so that the detected sound by the evaluation microphone 24 may be minimized. A correction means 36 detects phase deviations produced when the speaker 23 outputs an oscillation sound of 500Hz and corrects the transfer characteristics of a digital filter 33 and corrects the adjustment conditions if arithmetic operations by the adaptive filter 32 accordingly. This construction makes it possible to correct deviation produced during the execution of silencing operation in a real time in simple structure. |
