Algorithms for Adaptive Feedforward Noise Attenuation—A Unified Approach and Experimental Evaluation

Adaptive feedforward broadband noise compensation is currently used when a correlated measurement with the disturbance (an image of the disturbance) is available. Most of the active feedforward noise control systems feature an internal “positive” acoustical feedback between the compensation system and the disturbance measurement, which has to be taken into account. Adaptive algorithms for active feedforward noise attenuation have been developed since 1985 from a local optimization point of view. This article presents two classes of adaptive configurations for active feedforward noise compensation developed from a stability point of view. The first class uses a standard infinite impulse response (IIR) [finite impulse response (FIR)] compensator structure, while the second class uses the Youla-Kučera parameterization of the feedforward noise compensator. This allows separating the problem of stabilizing the internal positive feedback loop from the minimization of the residual noise. These adaptive schemes have been developed in the context of active vibration control, but, as will be shown, they can be used also in active noise control. This article presents, in a unified manner, the available algorithms and compensator structures for adaptive feedforward noise attenuation and provides a comparative experimental evaluation on a relevant experimental test bench (a duct silencer).