Abstract:

Time-reverse or phase-conjugate arrays (TRAs or PCAs) have been shown to retrofocus sound to the location(s) of its origin even when the acoustic medium and its boundaries are unknown. This retrofocusing is degraded by temporal variations in the acoustic environment. In this study, analytical predictions are made for the focal properties of a linear vertical time-reversing array in a stably stratified acoustic medium having sharp thermocline separating regions with two different sound speeds. The medium is assumed to be quiescent except for the presence of a deterministic soliton internal wave traveling along the thermocline. The soliton wave shape and propagation speed are obtained from the K--dV equation and relevant shallow-water oceanic parameters. Soliton motion is incorporated in the necessary two-way acoustic propagation formalism with the single-scattering approximation. Depending on the acoustic frequency and source-array range, current results suggest there is ample opportunity for successful TRA deployment in the presence of soliton internal waves. [Work sponsored by the Office of Naval Research.]