Modeling the acoustic channel for mixed pressure and particle velocity sensors.

Abstract

Looking at our repertoire of acoustic modeling techniques, ray tracing and Gaussian beams provide a good match to modeling the underwater channel for acoustic communications, given their fundamentally broadband nature. We will discuss how we have augmented existing acoustic models, including Gaussian beam and normal mode codes, to produce particle velocity predictions. In both of these cases, the modifications consisted of manipulating the components used to represent the pressure field, as opposed to relying upon a finite difference approximation of the predicted field itself. We will discuss further modifications to these codes that enable the dynamic features of the channel to be modeled, including source and receiver motion, and motion of the ocean surface due to ocean surface waves. It is important to model realizations of the channel, rather than averaged representations, because many of the high-speed, coherent modulation schemes that are the focus of continuing research use tracking loops in their design. These tracking loops must be stressed with realistically time-evolving channels. Acoustic channel predictions will be compared with experiment data from acoustic communications experiments off the coast of Kauai in Hawaii.