Hydrophone-Preamplifier Optimization

In any system, a number of hydrophone-preamplifier combinations are capable of meeting the design parameters; however, the choice of an optimum design is not always obvious. This paper presents an approach by which an optimum design may be obtained. Since the output signal-to-noise ratio of the preamplifier is a function of hydrophone sensitivity and capacity, which in turn are functions of hydrophone dimensions, it is apparent that an optimum hydrophone-preamplifier combination might be arrived at by combining preamplifier characteristics with hydrophone characteristics. This paper outlines a computer approach to this problem and shows the results. A typical case is presented that considers a multielement array where both size and weight are important. A set of equations and curves is generated whereby different sized hydrophones are placed under a common denominator and evaluated on a relative basis. Finally, these results are combined with a preamplifier producing a set of signal-to-noise output contours from which an optimum hydrophone-preamplifier may be selected. This concept has been proved on a recently completed project. One interesting result was the combination of a pair of hydrophones in series at the input of each preamplifier. This is contrary to normal practice of two units used in parallel addition.