RAYS AND MODES IN AN UNDERWATER CHANNEL WITH EXPONENTIAL VELOCITY PROFILE.

A newly developed theory is applied that utilizes a judiciously chosen mixture of ray fields and modal fields to represent the signal due to an oscillating line source at various depths, observed at different depth and range intervals. The ocean is modeled by an exponentially increasing sound velocity between the free surface and a homogeneous semi-infinite bottom. This environment combines surface duct and waveguide phenomena. The nature of the hybrid formulation for surface ducted fields and fields guides by top-bottom interaction is studied in detail, as is the possibility of choosing the ray-mode mixture so as to avoid corrections near caustics and cusps of the ray-acoustic pressure field.