Design and development of a high-power wideband multimode Tonpilz transducer for underwater applications

A multimode transducer is preferred for its broader bandwidth compared to traditional single-mode transducers. However, developing a wideband multimode Tonpilz transducer that operates at lower frequencies poses significant challenges. This study aims to create a high-power multimode Tonpilz transducer operating at 12 kHz with enhanced wideband characteristics by optimising the head mass radius. The devised transducer structure effectively incorporates two vibration modes: longitudinal and flapping, with the most simplistic head mass structure to maximise the fractional bandwidth (FBW) significantly. Further optimisation ensures a maximum bandwidth without compromising the transmitting voltage response. The variation of head mass structure and its impact on the transducer's overall performance was investigated using finite element analysis and experimental analysis. The optimised head mass radius was determined to be 85 mm, resulting in a highest FBW of 91.6% and a TVRpeak of 146.96 dB re 1mPa/V. Furthermore, the fabricated model with a head mass radius of 85 mm also exhibited a resonance frequency of 12.6 kHz, demonstrating good agreement between the finite element simulation and the fabricated prototype. Thus, the experimental validation by developing a prototype transducer ensures the efficacy of proposed structural design improvements.