Modelling, measurement and optimization of self-noise of hydrophone with preamplifier

Abstract

Self-noise is an important specification of hydrophone with preamplifier. This paper presents the modelling, measurement and optimization of the self-noise of hydrophone with preamplifier. Through analyzing various noise sources of hydrophone and its preamplifier, an effective self-noise model of hydrophone with preamplifier was established, and the self-noise was mainly affected by the hydrophone quality factor, preamplifier noise and thermal noise of preamplifier input resistance. In order to measure the self-noise of hydrophone with preamplifier, a measurement system was constructed and used for measuring the self-noise of a RHSA30 hydrophone which manufactured by Hangzhou Applied Acoustics Research Institute (HAARI) and has a typical sensitivity of -173 dB. After optimization of the self-noise of RHSA30 hydrophone, the measured equivalent noise pressure spectral density level was close to 30 dB at the frequency of 1000 Hz. The measurement results proved that the preamplifier current noise which mainly coming from the Operational Amplifier played a leading role at low frequencies of hydrophone with preamplifier. And some basic principles for self-noise optimization of hydrophone with preamplifier were given at the end.