Application of ray theory with beam displacement to three-dimensional sound propagation in a wedge-shaped ocean

Ray theory with beam displacement (RTBD) has been developed to evaluate the acoustic field in three dimensions in a wedge-shaped ocean with a lossy fluid bottom. An algorithm for tracing eigenrays in three dimensions is described. A procedure for determining the location of caustics in three dimensions is also presented. It is shown that the density of caustics reduces with increasing bottom attenuation. Sharp spurious peaks appear in the acoustic field in the vicinity of caustics. These caustic-related peaks can be readily identified and smoothed out, and no further corrections would be necessary in most situations of practical interest. Agreement between the smoothed RTBD solution and the ``exact'' two-way coupled-mode solution is quite good for the two-dimensional problem of up-slope propagation in the ASA benchmark wedge with a penetrable lossy bottom. Numerical results for the three-dimensional problem are presented for several bottom slopes and directions of propagation

Rotation sensitivity of Lau fringes: an analysis based on coherence theory

An analysis based on coherence theory is presented, which explains the experimentally observed rotation sensitivity of the contrast of Lau fringes obtained under spatially incoherent illumination