Ph.D. Proposal Presentation by Jie Yang
Tuesday, October 11, 2005

(Dr. Peter Rogers, Chair)

"Spatial Coherence in a Shallow Water Waveguide"

Abstract

Sound propagation in shallow water waveguide is a very challenging and complex problem. It's a mixture of physics, physical oceanography, marine geophysics, marine biology, and signal processing. The t emporal and spatial variations of the ocean make predictions of long range sound propagation difficult.

Many ocean characteristics can be modeled as stochastic processes. The statistical measure, spatial coherence, is thus an important quantity. Due to the complexity of the ocean environment, current research focuses on acoustical effects which are considered to be dominated by one of the three parts of the ocean: surface, bottom, and water column. It does not address the coupled effects of the three parts on measures such as the spatial coherence of long range sound propagation. In addition, there has been no systematic analysis of the spatial coherence pattern in the shallow water waveguide.

In this research, a more complete model for spatial coherence under the influence of the sea surface, bottom, and water column will be developed based on data collected from an at-sea experiment. The proposed research will be accomplished by (1) developing a sea surface roughness model based on the surface-wave-height spectrum; (2) using a three-parameter bottom model to show the effects of bottom sound speed and attenuation including the frequency dependence of the latter; (3) presenting a stochastic model for the shallow water internal waves; and (4) designing and performing a model experiment in a water tank to study acoustical effects of bottom type and surface roughness both individually and jointly.