Comments on “Complete Parallel Narrowband Active Noise Control Systems”

In the above paper Chang and Kuo show that the convergence of parallel narrowband active noise control systems is limited by the interaction between the multiple narrowband adaptive filters. To overcome this problem they propose a new algorithm that provides separate error signals to each of the narrowband adaptive filters, generated by filtering the error signal using bandpass filters tuned to the control frequency of each of the adaptive filters. Although these bandpass filters do not introduce an additional phase shift at the control frequency they do introduce an additional group delay into the secondary path. It is shown in this correspondence that although introducing these bandpass filters allows an increase in the step size it may also limit the convergence speed compared to the conventional algorithm.