A modified H-2 feedforward active control system for suppressing broadband random and transient noises

Abstract

Three feedforward active noise control algorithms based on H-2, H-infinity, and modified H-2 optimal model matching principles are investigated in this study. The first two methods provide significant attenuation for broadband random noises. However, the H-2 and H-infinity methods generally result in high-gain controllers at high frequencies, which calls for some truncation measures in the frequency domain. The third method effectively eliminates the high-gain problem of the ordinary H-2 and H-infinity algorithms. In addition, this method is guaranteed to result in a causal and stable controller which is crucial in practical implementation. The algorithms are coded into controllers by using a floating-point digital signal processor. The experimental results show significant attenuation for stationary broadband random noises as well as transient impact noises in a duct. (C) 1996 Academic Press Limited