Modeling intensity fluctuations of acoustic transmissions from the Research Vessel Sharp during Shallow Water 2006.

Abstract

During the Shallow Water 2006 (SW06) experiment, a J-15 source deployed from the University of Delaware’s R/V Sharp transmitted various acoustic signals at several different bearings and ranges to the Woods Hole Oceanographic Institution’s vertical hydrophone line array. The array was intentionally positioned near the shelf-break front and in an area where internal waves are known to occur. During several of the R/V Sharp’s acoustic transmissions, internal waves passed through the sound field such that the internal wave front was near parallel to the acoustic transmission path. Measured data show substantial intensity fluctuations that vary over time and space due to complex multimode and multipath (both two and three dimensional) interference patterns. This presentation provides an overview of the R/V Sharp’s transmissions and the corresponding intensity fluctuations of received signals at the array. In order to model the intensity fluctuations, a sound speed field is reconstructed using data from environmental sensors such as acoustic Doppler current profilers, ship radar, conductivity-temperature-depth profiles, environmental moorings, and satellite images. Measured data are compared to a simulated sound field computed by a three dimensional acoustic propagation model. [Work sponsored by the Office of Naval Research.]