Design and Implementation of a High-Sensitivity Inertial Cilium Combined Hydrophone for Low-Frequency Detection

Aiming at the insufficiency of hydrophones for high-sensitivity detection in the low-frequency domain, this article presents for the first time an inertial-type hydrophone encapsulating a microelectromechanical system (MEMS) stress-concentrated four-cantilever-beam piezoresistive accelerometer as a vector channel. At the same time, this inertial cilium combined hydrophone (ICCH) also integrates piezoelectric ceramic circular tubes as scalar channels. An inertial combined hydrophone package structure with an outer diameter of 63 mm combined with the theory of underwater sphere acoustic reception is designed. The chip of the ICCH vector channel is fabricated by the MEMS process, and the effective working frequency band is 10–630 Hz; the sensitivity in the X- and Y-directions are −175.1 dB@500 Hz −174.8 dB@500 Hz (0 dB =1 V/ $\mu $ Pa), respectively. Compared with the MEMS co-vibration combined hydrophone (CCH), the sensitivity is improved by 8.6 dB. The concave point depths are 44.1 and 43.5 dB, respectively, with good cosine directivity. The scalar channel sensitivity is −166.6 dB@500 Hz with omnidirectionality. The error of directional detection in the lake test experiment is less than 3°. The above results show that the hydrophone can meet the need for precise localization and has a broad application prospect in low-frequency hydroacoustic detection.