Analysis of the influence of turbulence and environmental variability on broadband acoustic coherence

Abstract

Acoustic propagation in the littoral regions of the world, even over short ranges, can be complex at high frequencies (>5 kHz), and applications such as underwater detection and communications suffer as a result. To this end, the Asian Seas International Acoustics Experiment (ASIAEX) was conducted with funding from the Office of Naval Research. One phase of this experiment took place from 29 May to 9 June 2001 and focused on short-range, shallow water acoustic propagation in the East China Sea. This thesis will be based on some of the measurements taken during the East China Sea experiment by a team from the Applied Physics Laboratory of the University of Washington. The environmental parameters and array geometry used in this and previous modeling work are as close as possible to the experiment. The objective of this thesis is to better understand the nature of turbulent perturbations and how they affect short-range acoustic propagation in a shallow water environment. This will include variations in total energy of the turbulence, variations in associated length scales, and variations in depth. In addition, the influence of other variable factors on signal coherence will also be examined. Most notably, variations in background sound-speed structure and source depth variability will be included.