Abstract
A hybrid active noise control (ANC) scheme for suppressing duct noise based on the H ∞ control synthesis is proposed. The controllers are designed in terms of performance, stability, and robustness using a general framework of the H ∞ robust control theory. In addition to the fixed controller, the system is further enhanced by introducing an adaptive compensator based on the least-mean-square (LMS) algorithm. Youla parameterization is employed in designing the adaptive compensator so that the resulting system is stable. Experimental investigations demonstrate that the proposed methods are effective in suppressing broadband random noise in a finite-length duct.