Broadband Model/Data Comparisons for Acoustic Propagation in Coastal Waters

Abstract

Broadband propagation data collected by SACLANTCEN in various shallow water areas in the Mediterranean Sea and in the North Atlantic have been modelled using a normal-mode propagation model. The data cover a frequency range of 50 Hz to 6.4 kHz, with experiments performed under a variety of different environmental conditions including seasonal changes in sound-speed structure, different sea states, varying water depth (90–300 m) and bottom composition with range, propagation through oceanic fronts, etc. Conclusions of the model/data comparisons are presented with emphasis on difficulties encountered (e.g. lack of environmental information), on detected model limitations, and on inferred conclusions concerning the actual environments. The importance of bottom rigidity (shear) as a low-frequency loss mechanism is evident in many model/data comparisons, particularly through its effect on the optimum propagation frequency, which is found to increase with increasing shear speed.