Edward F. Rynne
Naval Command, Control and Ocean Surveillance Ctr., RDT&E Div., 271 Catalina Blvd., San Diego, CA 92152
While impulsive acoustic sources have long been used by the geophysical community for underwater exploration, sonar applications have been relatively uncommon. Recent work in the area of electric discharge devices has led to both a better understanding of the physics of this class of impulsive sound generator and to new devices, which may in turn lead to an expanded role for such technology in sonar applications---in particular, the observation that the electric arc commonly associated with sparker sound sources represents a wasteful and unnecessary complication. Proper electrode design and control of the electric discharge can eliminate the arc, leaving only a steam bubble, and can thereby enhance the low-frequency performance of such a device. Insight into the performance and potential of such devices is, in part, a result of improved computer modeling capabilities of the nonlinear processes associated with impulsive devices, as well as on the use of high-speed data acquisition in interpreting experimental results. This is especially true for determining the effects of interactions in arrays of bubble sources. Beyond the electric discharge sources, understanding of the coupling of energy from the bubble to the sound field suggests improvements for chemically driven sound sources as well. An update of work on these impulsive devices and the modeling efforts that support them is presented. The performance of some recently developed devices and the potential for future development will be discussed.