Narrowland active noise control techniques
A narrowband active noise control (ANC) system with passband disturbance reduction and on-line secondary path estimation is developed in this thesis. The comb filter works parallel with the noise control filter and removes the outband disturbance for the noise control filter. The comb filter also performs as an adaptive noise canceller for the on-line estimation filter to enhance the convergence speed and estimation accuracy. Two reference signal generating techniques using the synchronization signal are presented. They are the pulse width adjustment method by directly processing the synchronization signal and the fundamental frequency estimation method by internally generating the sinusoidal signal. Theoretical analysis, computer simulations and the realtime implementation prove these two methods to be effective ways to generate the narrowband ANC system’s reference signal.