Improved energy-flux model for predicting range-averaged propagation loss in deep water

Abstract

A pocket calculator program has been developed to predict propagation losses smoothed over range in situations where energy incident on the bottom can be considered lost, as in many deep water scenarios at long ranges. Input parameters are range, source frequency, sound-speed profile gradients (assumed bilinear) and the sound speeds at source, receiver, channel axis, and bottom. To determine the effective channel depth, an extension of a familiar expression for propagation loss in a channel [D. E. Weston, J. Sound Vib. 18, 271–287 (1971)] averages over the rate at which ray paths intersect the receiver depth. The model also accommodates Lloyd mirror effects, some finite wavelength effects, and horizontal gradients of sound speed. Since individual ray paths are not considered, convergence zones and statistical fluctuations are not reproduced. Other limitations of the model, further simplifications, and cases in which it outperforms more familiar models will be presented.