A 2-D Electrochemical Velocity Gradient Hydrophone With Enhanced Sensitivity and High Directivity

The sensitivity and directivity of the hydrophone are the key factors governing localization accuracy in underwater target detection. However, current hydrophones show insufficient sensitivities and directivities at low frequencies. To address the limitations of existing designs, this study presents a novel integrated two-dimensional (2-D) electrochemical velocity-gradient hydrophone, in which enhanced sensitivities and high directivities are realized by optimizing the electrode-chip and sensor mechanical design. The device enables co-located, synchronous measurement of first-order (particle velocity) and second-order (velocity gradient) acoustic quantities over 20−630 Hz. It includes two first-order channels, one second-order pure-gradient channel, and one second-order mixed-gradient channel. The first-order channels exhibit an average sensitivity of −168.27 dB (ref. 1 V/μPa) across the operating frequency band and maintain a broad figure-eight directivity pattern. In contrast, both second-order channels demonstrate a sensitivity that increases at a rate of 6 dB per octave. Among them, the second-order pure-gradient channel achieves a sensitivity of −178.51 dB (ref. 1 V/μPa) at 630 Hz, which is 4.73 dB higher than that of the second-order mixed-gradient channel (−183.24 dB ref. 1 V/μPa at 630 Hz). In terms of directivity, the pure-gradient channel exhibits a narrow figure-eight pattern, while the mixed-gradient channel produces a four-lobe pattern. The results show that the proposed device exhibits enhanced directivity and improved low-frequency performance compared with conventional hydrophones, demonstrating its potential for underwater detection and localization.