Mitigating uncorrelated periodic disturbance in narrowband active noise control systems

This paper concerns the problem of uncorrelated periodic disturbance appearing at the error microphone in single-channel feedforward active noise control (ANC) systems. This disturbance, being uncorrelated with the primary noise, cannot be controlled by standard filtered-x least mean square (FxLMS) algorithm, and increases the residual noise. Furthermore, it significantly degrades the steady-state performance of ANC systems. Here we propose a new method which can simultaneously control both the correlated and uncorrelated noise signals. The proposed method comprises three adaptive filters; 1) the FxLMS algorithm-based ANC filter to cancel the primary noise, 2) a separate FxLMS algorithm-based ANC filter to cancel the uncorrelated disturbance, and 3) the LMS algorithm based supporting adaptive filter to generate appropriate signals for the two ANC filters. Computer simulations are carried out which demonstrate that the proposed method can effectively mitigate the correlated and uncorrelated primary disturbances, and gives significantly improved noise reduction performance. This improved performance is achieved at an increased computational complexity.