Parametric Studies of a Low-Frequency Underwater Transducer

Abstract

Low-frequency active transducers are essential for applications like active sonar, underwater communications, oceanographic studies, and underwater acoustic measurements. Different transducers, including free flooded rings, flextensional, flexural disks, Janus Helmholtz, and Janus Hammer Bell (JHB), are employed as low-frequency transducers. The JHB transducer features a double-headed Tonpilz transducer, known as a Janus driver, housed within a cylindrical structure. This transducer exhibits two resonances corresponding to the Janus driver’s length mode resonance and the cylindrical housing’s breathing mode resonance caused by the excitation of water trapped inside the cylinder. By adjusting these two resonances, a broad operating band can be achieved. This paper presents the modelling of a low-frequency JHB transducer with a resonance frequency below 1 kHz using commercial finite element software COMSOL. A comprehensive analysis was performed to investigate how changes in key parameters like the outer diameter of the piezoceramic stack, head mass, tail mass, housing, and the gap between the head mass and housing affect the transducer’s transmitting voltage response (TVR). The studies reveal that the outer diameter of the piezoceramic stack, head mass, and housing significantly influence the resonances. An optimised design was also arrived at based on parametric studies. The designed transducer can produce a
200 dB or higher source level at resonances.