A broadband multi-mode flextensional transducer with pressure compensation

• Novel transducer design integrates concave and convex shells for broadband performance. • Pressure compensation minimizes stress on piezoelectric elements in deep-sea conditions. • Ensures robust performance under deep-sea conditions with extreme hydrostatic pressure. • Suitable for low-frequency, long-range underwater communication and sonar detection. • Achieves stable acoustic performance with TVR > 125 dB across the 1.9–2.5 kHz range. Long-range target detection and underwater communication in deep-sea environments require compact, low-frequency projectors that are both broadband and resilient to hydrostatic pressure. This study introduces a novel broadband multi-mode flextensional transducer that integrates two types of radiating shells: a concave shell and a convex shell. The transducer achieves wide bandwidth and high source levels by leveraging the distinct resonance frequencies of the two shells, which are designed to operate in-phase regardless of the order of their resonance frequencies. A pressure compensation mechanism between the concave and convex shells minimizes stress on the piezoelectric elements, ensuring robust performance under hydrostatic pressures encountered in deep-sea applications. Finite Element Analysis (FEA) simulations revealed that the proposed design reduces the stress on the piezoelectric driver by over 85 % compared to conventional transducer models under high hydrostatic pressure. Experimental validation through lake tests confirmed the transducer’s broadband characteristics, with a transmitting voltage response exceeding 125 dB across the 1.9–2.5 kHz frequency band and response fluctuations of less than 6 dB. Excellent agreement between the FEA simulations and measurements underscores the precision and manufacturability of the proposed transducer design. This innovative transducer combines broadband performance and deep-sea operational stability, making it a promising solution for low-frequency, long-range underwater communication and detection in deep-sea environments.