Abstract
Concrete plinths are commonly used by engineers as a base for vibratory building services machines. However, it is not clear what effects they have on the structure-borne sound power transmission and the eigenfrequencies of floors. In this paper, the modal functions, eigenfrequencies, and mobility expression of a floor with a concrete plinth attached are deduced. The power transmissibility method is used to analyze the effect of a concrete plinth on the power transmissibility that is used to assess the performance of vibration isolation. It is found that the effect of a concrete plinth is mainly to decrease the eigenfrequencies of the floor, and changing the thickness of the concrete plinth has a greater effect on the eigenfrequencies of the floor and the power transmissibility than does changing the area of the concrete plinth. An estimated equation for power transmissibility is formulated.