Noise control system, non-transitory computer-readable recording medium including a program, and noise control method

A non-transitory computer-readable recording medium including a program for operating a signal processor mounted on a noise control system including a noise detector that detects a noise from a noise source to output a noise signal, a speaker that generates a control sound, and an error microphone that is provided at a control point and detects an interference sound of the noise and the control sound to output an error signal, the program comprising:

• by the signal processor by executing the program,
• causing a first control filter to perform signal processing to the noise signal to output a first control signal;
• causing a second control filter to perform signal processing to the noise signal to output a second control signal;
• outputting a third control signal by adding the first control signal and the second control signal;
• causing a transmission characteristic corrector having a transmission characteristic coefficient in accordance with a transmission characteristic from the speaker to the error microphone to perform signal processing to the noise signal on the basis of the transmission characteristic coefficient;
• updating, on the basis of an output signal from the transmission characteristic corrector and the error signal, a coefficient of the first control filter so as to minimize the error signal;
• and
• updating a coefficient of the second control filter, on the basis of an output signal from a first band limiting filter that performs a band limitation to the noise signal in such a manner as to fall within a predetermined frequency band and an output signal from a second band limiting filter that performs a band limitation to the third control signal in such a manner as to fall within the predetermined frequency band, so as to minimize the output signal from the second band limiting filter.

A noise control method to be executed by a noise control system including a noise detector that detects a noise from a noise source to output a noise signal, a speaker that generates a control sound, and an error microphone that is provided at a control point and detects an interference sound of the noise and the control sound to output an error signal, the method comprising:

• by a signal processor,
• causing a first control filter to perform signal processing to the noise signal to output a first control signal;
• causing a second control filter to perform signal processing to the noise signal to output a second control signal;
• outputting a third control signal by adding the first control signal and the second control signal;
• causing a transmission characteristic corrector having a transmission characteristic coefficient in accordance with a transmission characteristic from the speaker to the error microphone to perform signal processing to the noise signal on the basis of the transmission characteristic coefficient;
• updating, on the basis of an output signal from the transmission characteristic corrector and the error signal, a coefficient of the first control filter so as to minimize the error signal;
• and
• updating a coefficient of the second control filter, on the basis of an output signal from a first band limiting filter that performs a band limitation to the noise signal in such a manner as to fall within a predetermined frequency band and an output signal from a second band limiting filter that performs a band limitation to the third control signal in such a manner as to fall within the predetermined frequency band, so as to minimize the output signal from the second band limiting filter.