Abstract: A generally cylindrical hydrophone configuration provides compensation for longitudinal accelerations by placing four identical solid piezoelectric transducer elements along its axis with each transducer element being bonded to a head member, two of which are located generally centrally of the cylindrical housing and fastened thereto and two of which are located near the outside edges of the housing and having slight clearance therewith. Flexible polyurethane boots are clamped to the ends of the housing. The volumes between the centrally disposed and outer transducer head members and between the outer head members and the boots are filled with methyl silicon fluid. Each head member is electrically connected to one side of the electrical output, and the junction between the transducer members is connected to the opposite side, both sides being wired to an electrical contact plate located between the two centrally disposed transducer head members, this volume being filled with electrical potting material.

Abstract: A sonar system using closely spaced or interleaved projector and receiving transducer elements with a power inductor connected in series with the projector array transmits three separate frequencies and utilizes a resonant circuit connected across the projector array, and a switch alternately connecting the array to the transmitter or the resonant circuit. The resonant circuit has two parallel branches with an inductor in one branch and an inductor, a capacitor and a resistor in the parallel branch. An alternate embodiment includes a variable capacitor in series with the parallel circuit to simplify the tuning for individual installations. Values of the components were chosen to provide impedances looking into the resonant circuit which tend to maximize the "stiffness" of the projector elements for all the received frequencies, thus inhibiting the tendency of the projector elements to receive and reradiate echo signals during the receiving cycle of the sonar system.