Comparison of Multipath Arrival Structures Observed in the Presence of a Surface Duct with Predictions Obtained Using Classical Ray Techniques and the Parabolic Equation Method

摘要

Observations of multipath arrival structures made at sea using short pulses have indicated that energy leaking into and out of surface ducts can play a significant role in the propagation of acoustic energy. This leakage phenomenon was first reported with reference to leakage into and out of refracted-surface reflected (RSR) paths. Recent experience has indicated that this leakage phenomenon can also be of importance for energy propagating via bottom bounce modes. Observed underwater acoustic multipath arrival structures are compared with theoretical predictions based on historic sound speed profiles for the vicinity of the Mid-Atlantic Ridge (3500 m water) and the Blake Plateau (1000 m water). Examining these comparisons for surface duct environmental conditions resulted in the conclusion that wave theory is necessary for predicting the distribution of received energy and that classical ray theory (i.e., ray propagation using the high frequency assumption without sound leakage correction) is inadequate.