A study of the structure of electrohydrodynamic flows shows that the electric charge carriers are ions that are practically frozen into the surrounding liquid. In other words, ions in weakly conducting liquids are capable of forming more or less stable structures whose viscoelastic properties are different from those of an uncharged liquid. One method of studying this effect is to investigate the velocity dispersion of ultrasound on charged supermolecular formations. The results of theoretical and experimental investigations of acoustic dispersion in liquid dielectrics subjected to prebreakdown electric fields are presented. A model problem of sound propagation in a liquid in which supermolecular structures have formed around elementary charge carriers is studied theoretically. Approximate formulas describing the dispersion of the acoustic phase velocity as a function of the electric field parameters and the electrophysical parameters of the liquid are obtained. The frequency dependence of the sound velocity is of a resonance character, the resonance frequency being determined by the electric charge density and the mass of the charged supermolecular structures. The experiments showed that the space charge affects the velocity of acoustic waves in liquid dielectrics.