Abstract:
This thesis investigates the amplitude fluctuation effects in acoustic scattering due to shallow
water internal waves. Theoretically, it uses the adiabatic approximation and perturbation
methods to statistically evaluate acoustic transmission fluctuations caused by internal
waves in the ocean; it also investigates acoustic mode coupling effect due to internal
waves. Numerically, this thesis simulates the shallow water internal wave (IW) field using
the Garrett-Munk internal wave spectrum model and then evaluates acoustic transmission
in the simulated internal wave field with the Kraken normal mode program. Theoretical
calculations are also performed using the theory developed in this thesis. Comparisons are
made between theory and numerical calculations.
The results presented and discussed in this thesis are related to the following issues: coherent
and incoherent intensity fluctuations for adiabatic approximation, acoustic mode coupling
due to IW's, transmission loss difference between adiabatic and coupled mode
methods, and their dependence on range, IW amplitude and frequency.
