Experiments on Sound Propagation over Sloped Bottoms

Abstract

Experiments to study sound propagation in a shallow water wedge have been conducted in a tank. Results confirm the assumption of adiabatic normal mode theory that the mode shapes adjust continuously to the local water depth. Mode coupling, if it exists, is negligible. For upslope propagation, the energy of a mode travelling beyond its cutoff depth is directed into the bottom with negligible coupling to lower modes. For downslope propagation, the normal modes in a wedge propagate with curved wavefronts and not with the straight vertical wavefronts of simple adiabatic normal mode theory. In addition, normal modes not present at the source can be “captured” when the water depth is sufficient to support them.