Optimization of Active Noise Control for Small Axial Cooling Fans Optimization of Active Noise Control for Small Axial Cooling Fans

by Monson, Brian B

Previous work has shown that active noise control is a feasible solution to attenuate tonal noise radiated by small axial cooling fans, such as those found in desktop computers. One such control system reduced noise levels of a baffled 80-mm fan in the free field with four small loudspeakers surrounding the fan. Due to industry specified spatial constraints, a smaller fan and speaker configuration was desirable. The smaller configuration maintains similar control performance, further facilitating practical implementation of the control system. The smaller control system employs a smaller fan running at a higher speed. Different loudspeaker configurations for control exist and have been tested. A configuration consisting of four control sources spaced symmetrically around and coplanar to the fan exhibits global control of the tonal component of the fan noise. A configuration with three symmetrically spaced sources is shown to perform similarly, agreeing with theoretical prediction. An analysis of the control system in a non-ideal reflective environment is also discussed.