Noise Propagation Through Helicopter Gearbox Support Struts—An Experimental Study

[+] Author and Article Information
M. J. Brennan, S. J. Elliott

ISVR, University of Southampton, Southampton, Hampshire, UK

K. H. Heron

Air Systems Sector, Defence Research Agency, Farnborough, Hampshire, UK

J. Vib. Acoust 120(3), 695-704 (Jul 01, 1998) (10 pages) doi:10.1115/1.2893886 History: Received June 01, 1995; Revised March 01, 1997; Online February 26, 2008


A dominant source of noise in a helicopter cabin is the meshing of the gears in the main rotor gearbox. The main structural noise transmission path from this gearbox to the cabin is through the gearbox support struts, and this is the transmission path which is the subject of this paper. An experimental study is described which quantifies the way in which vibration propagates through one of these struts and the experimental results are interpreted with the aid of some simple analytical models. The contribution of the various modes of vibration to the transmission of the structure-borne noise is quantified by calculating the kinetic energy of the receiving structure from measured data. The results show that although the dominant mode of vibration is longitudinal, flexural resonances occur at some frequencies, and the contribution of the flexural vibration to the kinetic energy of the receiving structure at these frequencies can be comparable with that due to the longitudinal motion. It is demonstrated that the lateral behavior of the strut is dependent upon the static loading but the longitudinal behavior is relatively insensitive to this loading.

Copyright © 1998 by The American Society of Mechanical Engineers
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