Patent ID: 6768800
Filing Date: 2004-07-27
Classification: G10K

Abstract:
An active noise controller comprising:an additional sound source that produces a sound of a frequency substantially equal to that of an unnecessary sound among sounds emitted by an unnecessary sound source to reduce the acoustic power of at least the unnecessary sound; and a duct connected to the additional sound source to conduct a sound produced by the additional sound source; wherein the duct has an opening through which the sound emitted by the additional sound source is radiated, and the duct is formed such that the sound emitted by the additional sound source and having a phase substantially opposite to that of the unnecessary sound is radiated through the opening into the vicinity of the unnecessary sound source to cancel out and reduce acoustic power of the unnecessary sound when the opening is at a distance not greater than about half the wavelength of the unnecessary sound from the unnecessary sound source, and wherein a distance between the opening of the duct and the additional sound source is determined so that the duct resonates with the sound emitted by the additional sound source and having a frequency substantially equal to that of the unnecessary sound.