A simple method for estimating the dynamic properties of isolators is described. The experimental set-up consists of a seismic mass with isolators installed on an electrodynamic shaker. The method enables experiments with a relative wide frequency range and with different excitation levels. In this study, random and sinusoidal excitations are used and analysis is based on the acceleration signals at input and output sides of the isolators. The measured results of helical wire rope isolators are shortly presented.