Active noise control system

An active noise control system for attenuating an undesirable noise propagating from a noise source, the active noise control system including

• means for deriving an input signal representative of the undesirable noise;
• a digital signal processor programmed to operate as an adaptive filter for filtering the input signal in accordance with stored filter weighing coefficients to produce a filter output signal, the adaptive digital filter having a specified maximum filter output signal value above which filter output saturation occurs;
• actuator means for generating a noise canceling wave in response to the filter output signal and for superimposing the generated noise canceling wave with undesirable noise;
• means for sensing a residual noise level resulting from the superposition of the noise canceling wave and the undesirable noise and for developing an error signal representative thereof;
• means for adaptively adjusting the stored filter weighing coefficients based upon the error signal to reduce the sensed residual noise level;
• means for monitoring the filter output signal and for detecting the occurrence of filter output saturation based upon monitored values of the filter output signal;
• and
• means for computing an average power value for the filter output signal;
• means for estimating a power reference level, which represents a maximum for the average power value without the occurrence of filter output saturation;
• and
• means for modifying the adaptive adjustment of the stored filter weighing coefficients to decrease the filter output signal value in response to detecting the occurrence of filter output saturation based upon the difference between the power reference level and the computed average power value, when the computed average power exceeds the power reference level.