Performance of a Terfenol-D-driven folded shell projector

Abstract

The folded shell projector (FSP), U.S. Patent No. 5,805,529, is a compact flextensional transducer originally developed for low-frequency naval sonar applications. The FSP design radiates sound from a one-piece corrugated shell. Because the shell is inherently waterproof, the projector does not need a boot. This reduces cost, improves linearity, increases thermal conductance, and, most importantly, results in stable performance with depth. The folded shell projector is being evaluated for a number of applications including towed array and expendible sonar transducers, community warning sirens, and loudspeakers. A folded shell projector driven by the giant magnetostrictive material, Terfenol-D, has been developed. This transducer was originally designed for use as a community warning siren, however, tests both in air and in water were performed to investigate its response to different acoustic loads. Experimental results of the transducer performance are presented and compared with performance estimates from an equivalent circuit model. Limitations of the current design and the modeling efforts to improve it are discussed as well as plans for future development of the FSP.