Active control of an off-axis noise source

J. Guo, M. Hodgson, J. Pan


A multi-channel active-noise-control system can been used to create a large quiet zone in free-space when the noise source is on the symmetry axis of the control system. In this study, the efficiency of a multi-channel active-noise-control system is investigated numerically for the case of a noise source located at off-axis positions. It was found that both the location and the size of the quiet zone change significantly with the off-axis location of the noise source. The control system is still able to construct a large area of wavefront matching, and create a large quiet zone, when the off-axis shift of the noise source is within this range. There exists an off-axis range for which an optimally pre-arranged multiple-channel control system remains optimized. This range is expressed analytically in terms of the wavelength at the frequency of interest, and of the configuration of the control system.


Natural frequencies; Optimal control systems; Optimization; Wavefronts; Active control

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