Mark Grabb
Ted Birdsall
Dept. of Elec. Eng. and Comput. Sci., Univ. of Michigan, 1301 Beal, Ann Arbor, MI 48109
For long-range sound propagation simulations, ray tracing has many advantages as well as drawbacks. Some of the advantages ray tracing offers are 3-D implementation with present-day computers and the capability of propagating only the acoustic field that will contribute to a single early arrival. Well-known drawbacks to ray tracing computations are the neglect of diffraction effects, infinite-amplitude results at caustics, and the often quoted ``high-frequency approximation.'' However, other simulation techniques have advantages and drawbacks as well, suggesting the community should use many of the available propagation techniques and build strong conclusions through assimilation of results. Here, a ray-endpoint density method is investigated for calculating the time-domain amplitude of a received early arrival. Also, computation of the received time-domain phase is studied. The methods are investigated using 2-D range-invariant, 2-D range variant, and 3-D time and space variant computational ocean sound-speed models. The ray-endpoint density method is compared against normal mode, PE, and dynamic ray tracing results. [Work supported by ONR-ASSERT.]