Environmental Effects of Waveguide Uncertainty on Coherent Aspects of Propagation, Scattering, and Reverberation

Abstract

The robustness of the coherence of waveguide propagation to environmental uncertainty becomes an important consideration for systems that seek to exploit coherence for gain. Examples include matched field processing for passive localization and time reversal mirrors (TRMs) for active systems. Here, efficient normal mode representations of midfrequency time-domain propagation using the narrowband and adiabatic approximations are used to explore the deterioration of coherent active system predictability and performance in the presence sound-speed perturbations in the water column. Results show that for TRMs the reverberation level at the focal range is increased, and the scattering from an illuminated object is reduced for ensembles over oceanographic uncertainty. Results are obtained analytically as formal averages and are believed to represent a lower limit on the deterioration of TRM performance in the presence of environmental uncertainty for shallow-water waveguides.