Patent ID: 6078671
Filing Date: 2000-06-20
Classification: F01N,F02M

Abstract:
A silencer mounted on an air duct for attenuating a sound or noise transmitted through the air passage of the duct, comprising:a noise detecting microphone mounted on said duct for detecting said noise;a loud speaker mounted on said duct to deliver, on the basis of the noise detected by said microphone into said air passage, a sound which is substantially the same as said noise except that the phase of the sound is the reverse of that of the noise to thereby enable the sound to be superimposed on the noise to thereby attenuate the noise; andvibration shield provided between said microphone with a windscreen and the wall of said duct for shielding any vibrations to be transmitted through said wall to said microphone so that said microphone detects said noise without any noise interference caused by said vibrations.