Dept. of Ocean Eng., MIT, Cambridge, MA 02139
Over the last couple of decades significant progress has been made in modeling seismoacoustic propagation in shallow water. Thus, for example, environmental features such as a stratified, elastic bottom is a standard feature in several propagation models, even range-dependent ones with the development of the elastic PE. The past emphasis on deterministic propagation modeling has been driven by the primary interest in passive sonar systems for shallow water. However, with the increased importance of active sonar scenarios in shallow water, as well as the significance of acoustics for underwater communication, a wide range of new issues face the acoustic modelers. Thus, at the higher frequencies involved, the traditional wave theory models are not particularly efficient, and classical approaches such as ray tracing should be re-visited and modified to properly account for bottom interaction in particular. In addition, the spatial and temporal coherence becomes an important issue, in particular in relation to the oceanographic and geophysical variability, raising a need for stochastic seismoacoustic models. Another important issue is reverberation from the rough and inhomogeneous, elastic bottom. The various issues are illustrated using simulated and real data, and the associated needs for new mathematical and numerical models are discussed.