Active noise control using a dual feedforward approach

A dual feedforward controller for active noise control is presented. The first part of the controller is designed to cancel broadband noise, and the second part is an adaptive controller designed to cancel periodic noise. A simple technique to identify the parameters of the broadband controller is developed. An autoregressive moving-average model is used, and it is found that its stability is improved by prefiltering the test signal with a minimum-phase inverse of the secondary noise channel. The periodic controller uses an estimate of the fundamental frequency to cancel the first few harmonics of periodic noise. A computationally efficient adaptive technique based on least squares is developed to update the harmonic controller gains at each time step. Experimental results are included which demonstrate simultaneous cancellation of both random broadband noise and periodic noise