Contributions to the intensity field in shallow water waveguides

In a typical waveguide propagation, the acoustic intensity field is made up from contributions by a direct wave, bottom and surface reflected waves, and a number of interface waves. In shallow water environments, the laterally traveling headwave, generated by interaction with a faster propagating bottom layer, may become important. Several numerical techniques are used to calculate intensity fields in shallow water environments including normal modes, parabolic equation, and finite element methodologies. Bottom interactions are modeled with equivalent fluid properties, and the relative influence of the laterally traveling head wave is examined for several bathymetries of interest. Each codes' solution and merits are compared when calculating both propagating (active) and stationary (reactive) low frequency acoustic intensities.