Modeling study of underwater acoustic propagation over sand dunes in the South China

Abstract

There is an extensive field of underwater sand dunes located at depths between 160 m and 600 m in the northeastern South China Sea. The largest amplitude of these sand dunes is about 16 m with horizontal length scales between 200 and 400 m. Underwater acoustic transmission can be affected by these topographic features. Two-dimensional (2-D) and three-dimensional (3-D) underwater acoustic propagation models, RAM and FOR3D, were employed to simulate the acoustic propagation over these sand dunes from a moored source to a vertical-line hydrophone array deployed in an experiment in 2014. Environmental input to the models were the measured bathymetry and sound speed profiles. To prevent model over initializations at steep angles in an ocean with a high-impedance, low-loss bottom, the generalized Gaussian starter was employed and tuned to match the angular beam-pattern of the moored source to give a proper starting field. Simulation results pertaining to the temporal fluctuations, 2-D and 3-D propagation effect...