Exploiting natural surface noise and ships as sources of opportunity for passive bottom reflection-loss estimation

The marine ambient-noise field, including natural and anthropogenic sources, can be exploited to estimate the bottom reflection coefficient and the associated loss, which is an important contributor to the total transmission loss in shallow water scenarios. The physical nature of the natural surface-noise field is such that the bottom reflection coefficient can be estimated passively by beamforming on a vertical line array, if there are no localized sources near the array and the noise level generated by waves and wind is adequate. Recently, an algorithm for processing the noise generated by a single ship moving over a wide range of steering angles has been shown to extend the technique to this source of opportunity, even when the natural noise level is too low to produce any measurable loss. In this study, simulation and data from recent experimental campaigns (from arrays moored to the bottom or mounted on an autonomous underwater vehicle) are used to illustrate the technique, and investigate in particu...