Ray structure of the sound field in a waveguide with a gas-saturated sedimentary layer

Using ray approach analytical expressions for the calculation of sound field complex amplitude in a waveguide, where the bottom is represented as a gas-saturated layer laying on a liquid half-space, are derived. Sound speed in water is assumed to be not depending on depth. Rays are classified by quantity of reflection from upper and lower bounds. Ray branching caused by reflections from the bound between water and gas-saturated layer are considered. Using obtained expressions, the calculations of sound field for the 120-m depth waveguide with various sound speeds in sedimentary layer are carried out. The results of these calculations are compared with the results obtained by ray method for a waveguide with a bottom represented as a liguid half-space with the same parameters as the sedimentary layer. The thickness of gas-saturated layer at which we can neglect the influence of lower half-space is estimated.