Modeling Analysis and Experimental Verification of Tri-Axial Differential Pressure Vector Hydrophones Based on Piezoelectric MEMS Arrayed Sensors

This paper proposes a tri-axial acoustic differential pressure vector hydrophone, which consists of three pairs of piezoelectric MEMS sensors. The presented sensors are designed and fabricated using the AlN-on-CSOI MEMS platform, realizing an improving acoustic pressure sensitivity of 178.5 dB±2 dB (re 1V/μPa)@1kHz. The pressure-gradient receiving model of pairs of symmetrically distributed MEMS sensors in acoustic field is analyzed, guiding the structure design of the tri-axial acoustic differential pressure vector hydrophone. Calibrations in a standing wave tube are conducted. The effectively operating working frequency band for the presented vector hydrophone is within 20–2000 Hz. The acoustic sensitivities of the hydrophone for the three axes are −182.1 dB@ 1000Hz, -182.5 dB@ 1000 Hz and -182.8 dB @1000 Hz (0 dB = 1 V/μPa), respectively, with a maximum error of less than ±1 dB. Moreover, apparent “eight-shape” directivities for the three axes coupled with the concave point depths of 43.2 dB, 42.1 dB and 39.3 dB, and the asymmetries of 1.8 dB, 2 dB and 1.9 dB are demonstrated. The results indicate that the tri-axial differential pressure MEMS vector hydrophone holds promising prospects for low-frequency underwater acoustic detection applications.