An Automatic Acoustic Ray Tracing Computer

An automatic analog device for plotting sound ray trajectories in the ocean, and determining time of travel, is described, The basis of the machine is a small general purpose analog computer with only 17 operational amplifiers. It is capable of plotting long rays, and rays with surface reflections and bottom reflections. Vertical velocity gradients are accommodated, horizontal velocity gradients less conveniently. The machine has been tested and used and is completely successful, being reasonably simple to operate, as accurate as the approximations of the input data allow, and requiring only 10 to 15 minutes to produce a ray diagram from the appropriate oceanographic data. The computation involves the solution of a nonlinear second-order differential equation. The nonlinear oceanographic data are approximated by a series of straight line segments. Each segment is applied to the machine as a potentiometer setting, with automatic switching between the potentiometers. The velocity profile is represented by up to 25 layers of adjustable depth; this number could be increased with little effort. The surface and bottom reflections are automatic.