A cylindrical hydrophone with built-in amplifier

A low frequency hydrophone with built-in amplifier was presented. It used cylinder piezoelectric ceramic as a sensing element, which had been embedded by polyurethane. When sound pressure was applied to the flexible cylinder, the piezoelectric ceramic transferred the sound pressure to electric charge. There was a preamplifier in the hydrophone. The sensitivity of the hydrophone can be controlled by adjusting a load resistance in the preamplifier, the range of adjustable sensitivity was -190 dB to -170 dB (re 1 V/¿Pa), and the frequency response was 16 Hz to 20 kHz.