Properties of Sponge Rubber as a Material for Damping Vibration and Shock

In order to obtain vibration-proof mountings, use is frequently made of sponge rubber. In this paper investigations are described concerning the factors on which its vibration damping properties depend. Formulas have been deduced for the mechanical impedance of sponge rubber, taking into account the presence of pores in the material. The formulas render the results of the measurements satisfactorily and, at the same time, they show how the qualities depend on factors such as porosity, kind of rubber, size of the pores, dimensions, etc. Under Section 6 we have examined more closely the choice of sponge rubber and the way of utilizing it in order to obtain the best results. 1. General.—Sponge rubber appears to possess excellent qualities as a damping material. This being so, the question arises as to what part is played by the air it contains, and how this air content must be fixed to obtain the best results. We have attempted to answer this question by paying attention to the mechanical impedance of sponge rubber.