A high sensitivity and signal-to-noise ratio vector hydrophone combined with flexoelectricity and piezoelectricity

Currently, vector hydrophones typically employ arrays to indirectly measure higher-order sound pressure gradient signals, lacking direct and accurate methods for measuring the higher-order signals. In this work, we proposed a cantilever-type double-layer vector hydrophone combined with flexoelectricity and piezoelectricity. The bonding of two piezoelectric layers with opposing polarization directions along the thickness significantly enhances the surface polarization intensity of the core component during bending deformation caused by the excitation of sound waves. This configuration directly converts the sound pressure gradient from a plane wave into surface polarization charge. It enhances the effective flexoelectric coefficient and facilitates precise measurement of the sound pressure gradient amplitude. The experimental results show that the sensitivity of the double-layer vector hydrophone in the frequency range of 20-350 Hz closely matches theoretical predictions. In addition, the working bandwidth increases as the size decreases. This indicates that theoretical calculations can predict hydrophone configurations tailored to specific frequency bands and sensitivity limits. Furthermore, compared to the piezoelectric hydrophone (RHC-14), the double-layer vector hydrophone has a higher sensitivity and a signal-to-noise ratio in the experiments. The double-layer vector hydrophone exhibits symmetrical eight-shaped directivity and excellent resolution for sound waves in different directions. These results offer an alternative approach for vector measurement.