Influence of geoacoustic modeling on predictability of low-frequency propagation in range-dependent, shallow-water environments

In a previous study of predictability of relative intensity and horizontal wave numbers by the authors, parabolic approximations were used in range-independent shallow-water waveguides. Uncertainties in sediment properties were found to be the most significant factor limiting prediction accuracy. In this paper, models of bottom sound-speed profiles that take into account sediment consolidation are developed, and their effects on propagation model predictions in range-dependent environments are examined. Environmental parameters correspond to those near the site of a recent New Jersey Shelf experiment site. Using borehole density data and Biot–Stoll theory, a functional form for porosity in a homogeneous consolidated sediment is derived. Corresponding sound-speed profiles for different sediment types are then constructed. Predictions from models consisting of consolidated sediment layers throughout the bottom are compared with results from cases for which sound-speed is comprised of piecewise linear segments. In addition, bottom sound-speed range dependence was modeled with discrete as well as continuous changes between profiles for variations of the geophysical parameters in this area and no substantial difference was observed. Comparison of experimental data with model predictions incorporating range dependence are discussed. [Work supported by ONR.]