The present paper reports the results obtained from an experimental investigation carried out to study the dynamic responses of partially filled fluid tanks exhibiting a sloshing motion. A simple test rig has been developed to simulate
such a phenomenon using a horizontal harmonic excitation system. Both cylindrical and spherical tank shapes have been considered. Mechanical Impedance Data were acquired for the different system and operational parameters. These include the fluid mass, tank size, excitation frequency and force level. An equivalent linear viscoelastic model (modified Maxwell's model) has been adopted to represent the dynamic behavior of such systems. In addition, an imperical formula describing the fundamental frequency of the sloshing liquid in terms of the tank diameter and liquid height has been presented. High damping characteristics were observed for the tested system which make it suitable for vibration attenuation.