An active noise controller based on a constrained transform domain adaptive IIR filter

Active noise controllers often employ an IIR adaptive filter in order to compensate for acoustic feedback. Unfortunately due to the poor low frequency response of loudspeakers such IIR filter based controllers are highly susceptible to instability. In this paper a new active noise controller is presented that mitigates this instability. The controller is based on a novel transform domain adaptive IIR filter, termed the TRLMS filter. Using the TRLMS filter, the stability of the controller is improved by directly constraining the adaptation of the adaptive filter´s frequency response. A filtered-U adaptive algorithm for the constrained TRLMS filter is given. The stability of the TRLMS noise controller using two transformations is investigated through computer simulation.