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Title: Active tonal noise control for a computer cooling fan
Authors: Wang, J
Huang, L
Keywords: Noise control
Computer cooling
Dipoles (Electromagnetism)
Noise (Sound)
Drag (Fluid dynamics)
Acoustic interference
Issue Date: 2005
Source: Proceedings of the ASME 2005 Fluids Engineering Division Summer Meeting, Houston, Texas, USA, June 19–23, 2005, v. 1, paper no. FEDSM2005-77141, p. 465-474 How to cite?
Abstract: The noise sources on a blade can be divided into a thrust force component along the rotating axis, and a drag component on the fan rotational plane. The radiated noise is a result of acoustic interference among all blades, and the two source components. For a sample fan with B = 7 blades, and S = 7 struts, the drag noise is expected to cancel themselves out. The result is a simple thrust dipole along the fan axis. When B = 7 and S = 4, however, the dominant noise is a rotating drag dipole. This paper demonstrates, experimentally, the global elimination of the blade passing frequency tones from the thrust dipole and the rotating drag dipole for the two sample fans, respectively, by using a simple open-loop, feedforward control scheme. The rig consists of a miniature electret microphone used as a rotation sensor, ordinary loudspeakers, and a bandpass filter with adjustable amplitude and phase delay. The electret microphone is installed flush with the inlet bellmouth of the fan. It picks up the fluctuating aerodynamic pressure caused by the passing rotor blades, and is shown to perform much better than a normal optical tachometer.
ISBN: 0-7918-4198-7
0-7918-3760-2 (E-ISBN)
DOI: 10.1115/FEDSM2005-77141
Appears in Collections:Conference Paper

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