Dynamic modeling of 1–3 piezoelectric composite hydrophone and its experimental validation

Conventional hydrophones are usually used below their resonance frequency over a wide frequency band. Resent study showed that the hydrophones operated around the resonance frequency had potential applications in weak signal diagnosis for improving the sensitivity or resolution. However, the conventional hydrostatic model based on off-resonance hydrophone design is incapable of analyzing the hydrophones operated around the resonance frequencies, where the electromechanical response is changed sharply with frequencies. To expand the operating limits of the hydrostatic model, a dynamic model of fluid–structure interaction for analyzing the 1–3 piezoelectric composite hydrophones is presented. An analytical solution for output voltage of the hydrophone operated in thickness-stretch vibration is derived. This dynamic model is sufficient to analyze the 1–3 piezoelectric composite hydrophones over the entire frequency range, especially around the resonance. In addition, the output voltage obtained by dynamic model in the off-resonance range agrees well with those obtained by hydrostatic model. To verify the theoretical analysis, we fabricated a 1–3 piezoelectric composite hydrophone and experimentally measured the output voltage. Experimental results around the resonance show good agreement with the dynamic theory. The output voltage which peaks at the anti-resonance frequency as expected is of three orders of magnitude higher than that of conventional off-resonance hydrophones.