Compact High-Power Broad-Band Spherical PiezoCrystal Acoustic Source for Countermeasures

Acoustic countermeasures, deployed from ships and submarines, serve as decoys by mimicking the acoustic signature of the vessel. These autonomous devices require a highly efficient, high-power, broadband, compact acoustic source to achieve their goals. The combination of the most effective acoustic radiator design (i.e., a sphere) and the new high-coupling, high-strain relaxor piezocrystals provides an optimum combination to meet these exacting requirements. The technical challenge is to devise a cost-effective method of making a tiled approximation to a sphere. Other issues to be addressed, primarily by modeling, include specifically the actuation mode (d31 or d33) of the crystals, whether a fully active tiling is appropriate or whether some passive tiles should be included, and the implications of these choices for the drive electronics. In these applications both cylindrically and spherically shaped sources made from legacy piezoceramics have been employed with good results. Segmented cylinders of the relaxor piezocrystals provide a dramatic enhancement over the legacy piezoceramic cylinders, matching their acoustic performance in a package one hundredth the size requiring only half the energy. A tiled sphere (like a soccer ball) of piezocrystals will provide a similar step improvement over legacy piezoceramic technology.