Comparison between 31-mode and 33-mode Thin-walled Piezoelectric Tube Hydrophones

As the common configuration of hydrophone, the thin-walled piezoelectric tubes develop the two different modes, namely 31 mode and 33 mode. Their behaviors and the performances are studied, especially their receiving characteristics. A comparison about the sensitivity between 31 mode case and 33 mode case are presented based on the elastostatic theory and the finite element method. The approach to obtain the receiving voltage response in finite element analysis is introduced according to the electroacoustic reciprocity formula. Some hydrophone prototypes of 31-mode and 33-mode thin- walled piezoelectric tubes have been fabricated and the corresponding tests in the anechoic tank have been finished. The results show that 33-mode tube is capable of providing the sensitivity by approximately 20 dB higher than 31-mode tube with the similar size.