PREDICTION OF THE STRUCTURE-BORNE NOISE EMISSION OF MACHINES - DEVELOPMENT OF A METHODOLOGY

A method of estimating structure-borne emission of vibrating machines is described. It is shown that it is possible to calculate the emission of a resiliently mounted machine from three independent quantities; namely, the free velocity of the machine at the mount points, the dynamic stiffness of the mounts and the mobility of the seating. A full theoretical description of machines mounted at multiple points requires the evaluation of many terms, but the method can be simplified to yield a pair of formulae, one giving the mean emission and the other the standard deviation. Knowledge of the phases between mounting points is not required in order to arrive at an approximation to the emission and it is sufficient to use free velocities and mobilities which are averages over the mounting points. The method can be used to estimate emission for other degrees of freedom of machine motion, and it is shown that transmission by vertical translation is most significant at low frequencies but that via bending moments will become relatively more important at higher frequencies. The method described can be considered as a practical application of the free velocity method as described in proposed standards and extends the usefulness of such data. It allows an estimate of the structure-borne emission of resiliently mounted machines and an appropriate comparison of the structure-borne “noisiness” of practical installations. © 1993 Academic Press Limited.