Patent ID: 8411873

Claim:
A noise control device for reducing, by emitting a control sound toward a control point, a given noise arriving at the control point, the noise control device comprising: a controlling noise detector for detecting the given noise to output a controlling noise signal; a controlling filter section, including a fixed filter having a filter coefficient fixed therein, for signal-processing the controlling noise signal outputted from the controlling noise detector, in a state where the filter coefficient is fixed in the fixed filter, to output a control signal; a control speaker for reducing the given noise arriving at the control point, by emitting toward the control point a control sound based on the control signal outputted from the controlling filter section; a noise determination section for determining whether or not the given noise arriving at the control point is a noise corresponding to the filter coefficient of the fixed filter; and an output control section for stopping output of the control signal from the controlling filter section when the noise determination section determines that the given noise is not a noise corresponding to the filter coefficient of the fixed filter, wherein the noise determination section includes: a determining noise detector for detecting the given noise to output a determining noise signal; a determining filter section for signal-processing the controlling noise signal outputted from the controlling noise detector, using a fixed filter coefficient which is preset to reduce the determining noise signal outputted from the determining noise detector; an adder for adding the determining noise signal outputted from the determining noise detector and the controlling noise signal outputted from the determining filter section; and a level determination section for determining whether or not the given noise arriving at the control point is a noise corresponding to the filter coefficient of the fixed filter, by determining whether or not a level of an output signal from the adder is higher than a predetermined threshold, and the output control section stops the output of the control signal from the controlling filter section, when the level determination section determines that the level of the output signal from the adder is higher than the predetermined threshold.