The application of the finite‐element method of analysis to investigate the geometric and material factors which affect the open‐circuit voltage sensitivity of a class of underwater acoustic hydrophones is discussed. This class of hydrophones consists of an air‐filled, right‐circular, piezoelectric ceramic cylinder with flat nonpiezoelectric circular disk end caps. The study examines the factors which constrain the motion of the cylinder in a real hydrophone and cause the open‐circuit voltage sensitivity to be less than the value of an ideal hydrophone predicted by the equations developed by R. A. Langevin [J. Acoust. Soc. Am. 26, 421–427 (1953)]. Curves are presented to allow an estimate to be predicted of the reduction in the open‐circuit voltage sensitivity which a particular design will produce, and a comparison is made between these predictions and empirical data measured on various hydrophone configurations.