A Low Frequency MEMS Thermal Vector Hydrophone with Acoustic Velocity Horn

This paper presents a thermal vector hydrophone with an enhanced underwater acoustic horn package to detect low-frequency sound. The underwater package is optimized to significantly improve the sensitivity of the thermal vector hydrophone, considering both the boundary layer and the resonant interference from the structure at low frequencies. The test results demonstrate that the thermal vector hydrophone maintains a flat frequency response across the 10–1000 Hz range and achieves a sensitivity enhancement exceeding 10 dB. Additionally, the hydrophone exhibits a figure-eight directional pattern over the entire frequency range, with a null depth of 43.7 dB@3Hz.