Steven Finette
Dirk Tielbuerger
Stephen Wolf
Acoust. Div., Naval Res. Lab., Washington, DC 20375
The problem of the propagation of acoustic waves in a stochastic ocean
waveguide, for which the sound-speed variability within the water column is
treated explicitly as a random variable, is addressed. The sound speed is
composed of a deterministic, time-independent profile and two time-dependent
stochastic components representing a (linear) background Garrett--Munk internal
wave field and (nonlinear) internal wave soliton packets. A high-angle elastic
parabolic equation method is used to compute single-frequency realizations of
the pressure field using this representation of the sound-speed fluctuations.
Transmission loss and scintillation index measures are estimated for both the
full field and its modal decomposition at various ranges from the acoustic
source, for different source depths and for both flat and sloping bottoms. These
measures are incorporated in the analysis of acoustic modal coupling induced by
the internal wave fields as a function of range; results support a recent
prediction [D. Creamer, submitted to J. Acoust. Soc. Am.] that the scintillation
index increases exponentially with range due to the competition between mode
coupling and mode stripping found in shallow water waveguides. [sup