The Oceanographic Sensitivity of the Acoustic Channel in Shallow Water

This article analyzes the effects of key physical oceanographic conditions on underwater propagation in a shallow water environment. Signals at 2 kHz were transmitted and received over ranges of 1-10 km, and the variability in the sound-speed profile, bathymetry, position of the instruments, and sea surface roughness was measured and the uncertainty on each parameter was estimated. The acoustic channel characteristics, including the transmission loss, delay spread, and coherence time, were calculated between a moored five-element vertical line array and a vessel deployed source. The measurement results were modeled using a Bellhop's ray tracing algorithm. The sensitivity of the simulator output was evaluated as a function of the environmental conditions, and the observed variability in the transmission loss was reproduced by varying the input parameters to the model within the observed and estimated bounds. The relative importance of the physical properties of the environment in terms of their impact on the acoustic channel is determined through a comparison of modeled and measured transmission loss variability.