Insertion loss studies of a mechanical vibration isolation system

Abstract

Machinery noise control along the path can be classified into three approaches, namely, by enclosure, absorption, and vibration isolation. The transmissibility of a vibration isolation mounting is given by the ratio of transmitted force to foundation and the excitation force, whereas the insertion loss is obtained by the ratio of forces at the foundation without and with isolation mounting. The performance of a vibration isolation system is usually described using transmissibility which depends on the isolation system parameters with the machine considered as a rigid mass. However, the insertion loss of a vibration isolation system depends on the system parameters and source impedance, which accounts for the nonrigid characteristics of the machine. The nonrigidity of the machine can also be characterized through a base plate supporting the machine. This study deals with analysis of a system consisting of machine, isolation mounting, and rigid foundation in terms of insertion loss and transmissibility using a single degree of freedom model. Such studies would be useful in isolation mounting design for reducing machinery vibration and noise.