A general analysis of variable resonant frequency crystal systems which utilize liquid media as backing is presented. Formulas are obtained for evaluating the effect of different geometries of backing on the resonant frequencies of the system. The various loss factors associated with such a system are related to the measurable quantity, the quality factor.The observed operating characteristics of a variable resonant system which covers a two‐to‐one frequency band (40 kc to 80 kc) are presented. The results of an experimental comparison of such a system with fixed resonant frequency systems for generation of ultrasound in liquid media are given. The theory is used to correlate the experimental observations.