Underwater transducer

Abstract

An underwater transducer comprises a piezoceramic transduction layer and a etal substrate with a thin film of viscous fluid between them. The viscous film allows the transduction layer and substrate to expand and contract relative to each other when the laminate bends under increasing hydrostatic pressure as the transducer descends in a body of water. At sonic frequencies, however, the viscous film provides effectively a rigid bond between the transduction layer and the substrate so that they vibrate in unison. The invention reduces hydrostatic compressive loading on the transduction layer and thereby improves performance in deep water applications. A ring on the substrate surrounds and is engaged by the edge of the transduction layer as hydrostatic pressure increases in order to apply enough compressive stress to the transduction layer to prevent peaks in dynamic loading from exceeding the tensile limits of the transduction layer. Electrical connections are made to the face of the transduction layer opposite the face exposed to the viscous film. Viscosity effects are improved by the use of flow restricting structures. The invention can be embodied in a double bender disc transducer.