A new on/off scheduling for modeling secondary path in feedforward active noise control systems

A new technique is proposed for a controlled sound injection to model the secondary acoustic path in the feedforward active noise control (ANC) system. In the proposed system, the tap weights of the adaptive filter for modelling the secondary path are replicated to an additional filter, and a cost function for determining the opening and closing of the sound injection is evaluated with the difference of the powers of errors from both filters. If the acoustic characteristics are altered in the secondary path after closing the sound injection, the detection of outliers in the error from the modelling filter will provide a clue for reopening the injection. In this paper, the authors propose a simple algorithm to open and close the sound injection for modelling the secondary path. The results of numerical simulations show that the proposed technique improves the performance of noise cancellation without relying on the adaptive algorithms most often used in ANC systems.