Active noise control system

摘要

A active noise control system having a digital signal processor programmed to function as adaptive digital filter with an output saturation control is described. The programmed adaptive filter has a specified maximum value for its output signal, above which the output signal becomes clipped and a condition commonly known as filter output saturation occurs. According to the described system, the filter output signal value is monitored to detect the occurrence of filter output saturation. When output saturation is detected, the normal adaptation of the filter is modified to reduce the value of the filter output signal to prevent the further occurrence of filter output saturation. Based upon the detection of filter output saturation, a power reference level is established to estimate the maximum average power that the output signal can contain without causing saturation. The adaptation of filter weighting coefficients is then scaled in accordance with the difference between the established power reference level and a computed average power associated with the filter output signal to prevent the occurrence of filter output saturation.