Noise control device

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
• a plurality of the controlling noise detectors are provided,
• the controlling filter section is provided with a plurality of fixed filters which have fixed therein filter coefficients associated with the plurality of the controlling noise detectors, respectively, and the controlling filter section signal-processes the controlling noise signal outputted from each of the plurality of the controlling noise detectors, using a corresponding one of the filter coefficients, which are associated therewith, and fixed in the plurality of fixed filters, to output a control signal resulting from the signal-processing,
• the control speaker reduces the given noise arriving at the control point, by emitting toward the control point the control sound based on the control signals from the controlling filter section,
• the noise determination section includes:
• a determining filter section for signal-processing, using a plurality of fixed filter coefficients which are preset to reduce the controlling noise signal from one of the plurality of the controlling noise detectors and to be associated with the others of the plurality of the controlling noise detectors, the controlling noise signal from each of the others of the plurality of the controlling noise detectors;
• an adder for adding the controlling noise signal from the one of the plurality of the controlling noise detectors and the controlling noise signals from the determining filter section;
• and
• a level determination section for 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 signals 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.

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 determines whether or not the given noise arriving at the control point is a noise corresponding to the filter coefficient of the fixed filter, by receiving noise information which uniquely specifies a frequency and/or a level of the given noise arriving at the control point, and by determining, based on the noise information, whether or not a variation amount of the frequency and/or the level of the given noise arriving at the control point is larger than a predetermined amount, and
• the output control section stops the output of the control signal from the controlling filter section when the noise determination section determines that the variation amount of the frequency and/or the level is larger than the predetermined amount.

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;
• 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;
• an error detector, provided at the control point, for detecting a combined signal generated by combining a noise and the control sound from the control speaker;
• a signal storage section for storing the controlling noise signal detected by the controlling noise detector and an error signal detected by the error detector;
• a filter coefficient calculation section for calculating the filter coefficient for the fixed filter of the controlling filter section, by using the controlling noise signal and the error signal, both stored in the signal storage section;
• and
• a filter coefficient update section for updating, at a predetermined timing, the filter coefficient set in the fixed filter of the controlling filter section, to the filter coefficient calculated at the filter coefficient calculation section.