Development of a broadband Class III flextensional hydrophone

Class III flextensional transducers have been widely used as low-frequency projectors, but their characteristics also make them promising candidates for broadband low-frequency hydrophone applications. In this study, we propose a design of Class III flextensional hydrophone featuring significant structural modifications to achieve wider receiving bandwidth and higher sensitivity in the low-frequency range. Traditional hydrophones often increase bandwidth by reducing size-a straightforward and effective approach. However, this comes at the cost of reduced receiving sensitivity, as sensitivity is generally proportional to the hydrophone's surface area. To overcome this limitation, we developed a wideband hydrophone design that maintains a similar physical size, thereby preserving high receiving sensitivity. We constructed finite element analysis models of the Class III flextensional hydrophone to investigate how various structural parameters influence its acoustic receiving characteristics. Based on the simulation results, we determined the optimal combination of the parameters to maximize bandwidth while keeping the first receiving-voltage-sensitivity peak within a specific frequency range. The designed hydrophone demonstrated a fractional bandwidth 2.51 times greater than that of the conventional model, while maintaining a comparable receiving voltage sensitivity level.