Abstract:

A time-reversing array (TRA) can retrofocus acoustic energy to the location of its original source even when the acoustic environment is complex and unknown. However, predictions of array retrofocusing performance require an acoustic propagation model for the environment. Results are presented from a study of the sensitivity of TRA retrofocusing to acoustic propagation modeling. Results from a modal sum propagation model and a parabolic equation (PE) code (RAM by M. D. Collins) are compared for a perfect waveguide. The influence of waveguide complexity on retrofocusing is determined by adding range dependence and realistic bottom properties to the computed PE fields. Variations in acoustic frequency and sound source depth are also explored. It is found that acoustic penetration into the bottom primarily influences sound pressure levels but does not strongly influence the size of the TRA retrofocus. In addition, small changes in the waveguide's range dependence are found to have little effect on retrofocus properties. [Work supported by the Office of Naval Research.]