To provide an active noise controller in which a highly precise control effect is obtained using an analog low pass filter having a high cutoff frequency with a gentle cutoff characteristic, a howling phenomenon is reduced and the precision in the control effect in the control object frequency range is improved.
The controller muffles the noise propagated in a duct by radiating sound waves which are controlled by detection outputs of a first sensor 61 that detects the noise propagating in the duct and a second sensor 68 that detects the muffling condition in the duct and radiating the sound waves having phases opposite each other and the same sound pressures with each other from a speaker 67 against the noise propagation in the duct. A porous sound absorbing materials 22 are placed among the sensors 61 and 68 and the speaker 67 and the duct's inner wall surface corresponding to the duct's radial length at the upstream side of the sensor 61 so that the inner wall of the duct surface becomes flush.
ITO SHUICHI
TANAKA YASUNOBU
AOKI MASAO
