A High Sensitivity MEMS Omnidirectional Hydrophone Based on a Vortex-Slit Structure

This paper presents a novel vortex-slit piezoelectric MEMS omnidirectional hydrophone (VSOH). The vortex shaped slits are arranged in a twisted vortex pattern and distributed across the VSOH. These slits divide the membrane into four sub-membranes, which are connected by annular springs. This design improves stress distribution within the central region and controls vibration amplitude, thus protecting the membrane. Additionally, the vortex-slit can reduce residual stress and effectively suppressing the low-frequency roll-off (LFRO) effect, thereby improving sensitivity. In the range of 20–1000 Hz, its sensitivity is 6 dB higher than RHS(A)-20 and 15 dB higher than the B&K8104 with the highest sensitivity of −162.7 dB at 250 Hz. Furthermore, the VSOH demonstrates excellent omnidirectional characteristic, with vertical directivity of $360^{\circ}\pm 0.1\ \text{dB}$ at 630 Hz, enabling uniform responses to sound waves from any direction.