An Active Noise Control System for Impulsive Noise Using Soft Threshold FxLMS Algorithm with Harmonic Mean Step Size

One of the effective technique to limit most of the unwanted noise irrespective of noise-frequency component is Active noise control (ANC) system. Filtered-x Least-Mean-Square (FxLMS) algorithm based on step-size parameter is used in ANC method to control noise. ANC system with small step size are stable than with large step size since large step size leads to sensitivity to any random change in noise. The proposed method develops a novel soft threshold based FxLMS (STFxLMS) algorithm with harmonic mean based variable step size (HMVSS). By constantly changing the step-size of this algorithm corresponding to the input noise signal and error signal recorded from the error microphone, the convergence rate of ANC system towards the desired output was improved. The improvement in noise reduction using HMVSS compared with fixed step was demonstrated using computer simulations. Anti-noise signal was also generated experimentally to limit the noise from noise source.