Acoustic characterization of harbors and ports.

Abstract

The use of acoustics has become increasingly important in shallow waterways including ports and harbors. Applications span a range of military, commercial, and recreational interests including mine detection, port protection, and diver interaction. Harbor environments present challenges to acoustic propagation that are not encountered in the deep ocean or more open shelf environments. Characteristics that contribute to the unique acoustic propagation characteristics include typically very shallow depths, highly variable ambient noise levels, the presence of strong scatterers, and tidal effects. In a typical harbor, even a 1‐ or 2‐m tidal variation can represent a change of 10% or more in the water depth. In this work, in situ measurements of low‐frequency acoustic propagation are presented for a harbor near Newport, RI. The objective was to assess the propagation channel from a finger pier in a confined harbor out to the main shipping channel in Narragansett Bay and incorporate the findings into acoustic propagation models for this and similar environments. Of particular interest are the effects of tidal variations and changing background noise levels on the ability to detect different signals. [Work supported by ONR.]