Comparison of active noise control structures in the presence of acoustical feedback by using the H-infinity synthesis technique

Abstract

This study compares three control structures of active noise cancellation for ducts: feedback control, feedforward control, and hybrid control. These structures are compared in terms of performance, stability, and robustness by using a general framework of the H-infinity robust control theory. In addition, the H-infinity synthesis procedure automatically incorporates the acoustic feedback path that is usually a plaguing problem to feedforward control design. The controllers are implemented by using a digital signal processor and tested on a finite-length duct. In an experimental verification, the proposed controllers are also compared with the well-known filtered-u least mean square (FULMS) controller. The advantages and disadvantages of each ANC structure as well as the adverse effects due to acoustic feedback are addressed. (C) 1997 Academic Press Limited.