Propagation of low-frequency sound through densely sampled internal waves.

Abstract

It is well known that nonlinear internal gravity waves can have a significant effect on acoustic propagation. In particular, horizontal refraction and ducting of sound can occur when the acoustic propagation path is aligned with fronts of internal waves. Additionally, more complicated effects are associated with internal waves that are curved and/or truncated. In this talk, observations of internal waves measured on the New Jersey shelf area of the north Atlantic and their effects on the acoustic field are presented. During the experiment, a low-frequency source broadcasting continuous tone was towed repeatedly out and back along radials with respect to a VLA. The ship’s track was oriented parallel to the shelf break so that the acoustic propagation path was roughly aligned with internal waves propagating up the shelf. Internal waves were measured at the location of the receivers by temperature sensors on the VLA, at the location of the source by a towed CTD chain, as well as by a cluster of 16 environmental moorings located adjacent to experiment site. The high-spatial sampling of the environment allows for identification of range-varying features of internal waves.