William C. Ward
Los Alamos Natl. Lab., MEE-13, MS J576, Los Alamos, NM 87545
Thomas B. Gabrielson
NAWC, Warminster, PA 18974
Thermoacoustic generation of sound underwater represents a technology distinctly different from conventional underwater transduction. By proper design, there is potential for high-power, low-frequency generation of continuous-wave, pulsed, or modulated output. From a materials point of view, there are three major components: the stack, which maintains the temperature gradient responsible for pumping the acoustic oscillations; the working medium, which supports the internal acoustic oscillations; and the heat exchangers, which supply energy from an external source to the stack. Each of these subsystems has critical thermal and acoustical requirements that constrain the selection of materials and the overall source configuration. Thermal conductivity, viscosity, and specific heat replace piezoelectric constants and stress-strain relationships as fundamental properties. In addition, the acoustic performance is modeled more effectively as a waveguide than as a lumped-parameter system. Many of the advantages and disadvantages of this source technology are readily apparent in the context of materials selection and configuration. [Work supported by the Naval Space and Warfare Systems Command, PMW-183.]