Effect of Merging of Ray and Diffraction Caustics in a Refracting Oceanic Waveguide

We consider the patterns manifesting themselves in the formation of the spatial distribution of the intensity of an acoustic field excited by a point source emitting a tone signal in a deep-water oceanic waveguide with an underwater sound channel open to the surface and an acoustically transparent bottom. It is shown that at a certain emission frequency, the diffraction and ray caustics can merge, which leads to an appreciable increase in the acoustic field intensity along characteristic caustic lines on the horizontal distance–depth plane.