Noise control of subsonic axial fan in a duct

20th International Congress on Sound and Vibration 2013, ICSV 2013, Bangkok, 7-11 July 2013This study examines the Performance of the conceived device, which was tested under the no-flow condition [J. Acoust. Soc. Am. 132, 1392-1402, 2012] on Controlling the subsonic axial fan noise practically. This device consists of two tensioned membranes backed with cavities housing the axial fan. Noise reduction can be achieved by the destructive interference between the sound fields from axial fan with dipole nature and sound radiation from the membrane via the vibroacoustic coupling. A two dimensional model with the flow effect is presented which allows the device to be explored analytically. Experimental study of the real axial fan has been conducted to validate the analytical prediction. The flow effect is found to excite the odd mode response of the membrane by even mode Vibration due to kinematic coupling. This result in slightly deteroriation of the insertion loss spectrum at some frequencies and the peaks are smooth out. This is similar to the results given by the off-centre arrangement of the dipole source due to the asymmetrical acoustic pressure excitation. With the design of two membranes under 300N covered by two rectangular cavities, the noise radiation of the fan can be reduced by 20dB at the first blade passing frequency. A prototype involving four membranes with a cylindrical cavity has also been examined to demonstrate its feasibility practically.Department of Mechanical EngineeringRefereed conference pape