Noise control system and method

A noise control system comprising:

• a noise detector for detecting a noise generated from a noise source to output a noise detection signal;
• an adaptive filter portion for outputting a control signal based on the noise detection signal to cancel the noise;
• a control loudspeaker for receiving the control signal to radiate a control sound to a predetermined region;
• and
• an error detector for detecting a residual error of the noise and the control sound in the predetermined region,
• wherein the system further comprises filter control means for outputting a coefficient adjustment signal to control the adaptive filter portion, and
• the adaptive filter portion comprises:
• an adaptive filter for receiving the noise detection signal and processing the noise detection signal to output a control signal;
• an adaptive IIR filter means for receiving the noise detection signal, performing a filtering process to the noise detection signal according to a frequency characteristic determined based on with the coefficient adjustment signal, and outputting a first processing signal;
• operation means for receiving the first processing signal and performing convolution with a predetermined transfer function, and the first processing signal to output a second processing signal, the predetermined transfer function being determined based on control transfer characteristic from the control loudspeaker to the error detector;
• and
• multiplying means for receiving the second processing signal and the error signal, multiplying the second processing signal by the error signal, and outputting an update signal for updating coefficients of the adaptive filter to the adaptive filter.

An active noise control method for canceling a noise with a control sound, the method including:

• a step of detecting a noise generated from a noise source to produce a noise detection signal;
• a signal processing step of subjecting the noise detection signal to a filtering process with predetermined filter coefficients and producing a control signal to cancel the noise;
• a step of radiating the control signal from a control loudspeaker to a predetermined region as a control sound;
• and
• a step of detecting a residual error of the noise and the control sound in the predetermined region to produce an error signal,
• wherein the signal processing step includes the steps of:
• subjecting the noise detection signal to a filtering process with a predetermined frequency characteristic to produce a first processing signal;
• performing convolutions with the first processing signal and a predetermined transfer function to produce a second processing signal;
• multiplying the second processing signal by the error signal to produce an updating signal for updating the predetermined filter coefficients;
• and
• processing the noise detection signal with filter coefficients modified by the update signal to produce a control signal,
• the predetermined frequency characteristic and the predetermined transfer function being determined based on a control transfer characteristic from the control loudspeaker to the predetermined region.