Splitting frequency components of error signal in narrowband active noise control system design

A narrowband active noise control (NANC) structure is often applied to reduce undesired noise when multiple tones have close frequencies. A parallel ANC structure is proposed for separating undesired harmonics into a series of adaptive filters. Since the input signal of each adaptive filter has only one harmonic component, a second-order finite impulse response (FIR) filter is sufficient for processing the undesired noise. Therefore, the presented parallel structure for NANC system is greatly simplified. Based on the input signal frequency, a bank of bandpass filters splits the frequency components of the error signal to update the corresponding adaptive filters in the parallel NANC structure, each of which is computationally very simple and unaffected by time delay. A new performance index for a parallel NANC is also proposed. The increased convergence speed obtained by the proposed method is first confirmed by theoretical analysis. Computer simulations are then performed to confirm the enhancement.