Effect of a random ocean current on acoustic propagation

Abstract

The effects of a random current on the fluctuations of an underwater sound transmission are considered for a horizontal isospeed channel. The current is assumed to have a constant unperturbed part, plus small depth-dependent random variations in magnitude and direction. Using ray theory the current influence on ray geometry, travel time, spreading loss, and boundary effects is investigated. Then consistent approximations to total-field phase and amplitude at a fixed receiver are obtained. Acoustically pertinent statistics, including the mean and variance of total-field phase, are found as functions of the statistics of the current fluctuations. Conversely, it is shown how statistics of the assumed current structure can be described in terms of the total-field phase statistics. This initial study provides a basis for future investigations which will utilize more elaborate current and sound-speed models. [Work supported by ONR.]