Hydrophone
-173 dB, 1 V/μPa | Type 8106 Bruel and Kjaer

Type 8106 has a built-in amplifier which gives a signal suitable for transmission over long cables. It is usable down to 1000 m ocean depth
A wide-range, general-purpose transducer for making absolute sound measurements over the frequency range 7Hz to 80 kHz with a receiving sensitivity of −173dB re 1V/μPa. The hydrophone is capable of withstanding high static pressure, the operational upper limit being 107 Pa (100 atm.; 1000 m (3250 ft.) ocean depth). A built-in high-quality, thick-film, low-noise, 10 dB preamplifier provides signal conditioning for transmission over long underwater cables. The preamplifier features a 7Hz high-pass filter and an insert-voltage calibration facility, but does not allow the hydrophone to be used as a projector. An integrated watertight connector allows quick disconnection of the cable and makes replacement and storage very easy.