Acoustic noise interferometry in the Straits of Florida at 100 m depth: A ray-based interpretation

Cross-correlation function of ambient and shipping noise recorded simultaneously by two hydrophones provides an estimate of the acoustic Green's function, which describes deterministic sound propagation between the hydrophones and can be used to estimate physical parameters of the water column and seafloor. This paper presents results of an experimental investigation of acoustic noise interferometry in 100 m-deep water in the Straits of Florida. Acoustic noise was recorded continuously for about six days at three points near the seafloor. Coherent acoustic arrivals are successfully identified in the 20–70 Hz frequency band for pairs of hydrophones separated by ranges of 5.0 and 9.8 km. The measured noise cross-correlation functions are compared to ray-based simulations of Green's functions, with generally good agreement between correlation functions and simulations. Ray-based simulations are shown to reproduce multipath features of the measured correlation functions, which are due to multiple surface and bottom reflections. The feasibility of passive acoustic remote sensing using a few hydrophones in a shallow-water waveguide will be discussed. [Work supported by NSF, ONR, and NAVAIR.]