R. A. Fulford
B. M. Gibbs
Acoust. Res. Unit, School of Architecture and Bldg. Eng., Univ. of Liverpool, P. O. Box 147, Liverpool L69 3BX, UK
The structure-borne sound emission from machines through multiple contact points is highly influenced by the extent of coupling between these points. When the machine is unconstrained (i.e., disconnected from the supporting structure) the coupling can be assessed by comparing the point and transfer mobilities of the machine. Once connected however, account must be made too of the force distribution amongst the contact points. While the forces themselves at the points are sensitive to the structural characteristics of the particular installation, their distribution, which is most readily described by the ratios of the contact point forces, may be less sensitive. Using combinations of real and theoretical installations, force distributions have been investigated. Studies have also been undertaken on the estimation and approximation of the force ratios and their effect on the estimate of the total active power from the machine to the supporting structure. It will be shown that this has application to the characterization of structure-borne sound sources.