A decoupled hybrid structure for active noise control with uncorrelated narrowband disturbances

In real active noise control (ANC) applications, the following situations frequently occur, one is that disturbances only present at the error sensor and have low correlation with reference signal, the other is that there is no enough space or ideal position for locating the reference sensor to satisfy causality condition. Thus the residual noise after feedforward control can be seen as uncorrelated narrowband disturbances in these situations and a hybrid adaptive feedforward and feedback structure is often utilized to cope with this problem. Many efforts have been paid to improve the performance of the hybrid ANC system, nevertheless, few interests are concerned about the combination method between the feedforward and feedback structure. After investigating the conventional combination method of hybrid feedforward and feedback system, this paper introduces an alternate combination method for hybrid ANC system which features that it avoids the coupling between the feedforward and feedback structures and both structures are concatenated to attenuate the ambient noise. Simulations are carried out to validate the effectiveness of the introduced method for ANC with uncorrelated narrowband disturbances.