An electrochemical velocity-type vector hydrophone for high-sensitivity underwater acoustic detection below 100 Hz

Abstract

This paper presents an electrochemical velocity-type vector hydrophone designed for the direct detection of acoustic particle velocity. Compared to acceleration-type vector hydrophones, the proposed device demonstrates superior low-frequency sensitivity, effectively meeting the detection requirements for underwater acoustic signals below 100 Hz. A theoretical model was developed to analyze acoustic transmission characteristics and optimize the key parameters of the rubber membrane. The sensitive electrode chip, fabricated utilizing MEMS technology, integrates both cathode and anode electrodes separated by a 10 μm insulating spacer. The influence of different sensitive electrode configurations on the hydrophone’s frequency response characteristics was investigated using a water standing wave tube calibration system. Experimental results reveal that an electrode configuration with an 80 μm flow hole diameter exhibits optimal performance. Furthermore, a packaging design incorporating stabilized-flow channels was developed. Compared to conventional packaging, the proposed design with four stabilized-flow channels reduces the steady-state recovery time by 98 %. This design effectively isolates acoustic signals from fluid disturbance signals, significantly enhancing the hydrophone’s overload resistance in complex underwater environments. The hydrophone exhibits a flat amplitude-frequency response below 100 Hz, with a sensitivity of −172.6 dB at 5 Hz. It demonstrates good cosine directionality, with a concave point depth of −33.41 dB at 35 Hz. The device’s noise level was measured as 78.2 dB at 5 Hz on the bedrock of the seismic station. These characteristics highlight the hydrophone’s potential for detecting weak low-frequency underwater acoustic signals, making it well-suited for marine exploration applications.