Active noise control of a duct using robust control theory

In this paper the control of sound propagation in an air-handling duct using a feedback active noise control (ANC) system is investigated both from a theoretical and from a practical point of view. Using identified discrete-time models of the duct, robust linear controllers are designed by means of the combined pole placement/sensitivity function shaping method. The specific features of the harmonic sources of noise and the study of the effect of model uncertainty on the ANC performance are taken into account in order to avoid the classical stochastic adaptive and the reference noise-based methods. As a consequence, our solutions are easy to implement in real-time applications. As an illustration, we give detailed results for the control of the noise in an industrial air conditioner propagating through a duct.