High Frequency Acoustic Propagation and Modeling in Stratified Estuaries

Nicholas Swanda, S.M., 2022
Andone Lavery, Advisor

Acoustic propagation measurements are made in a highly variable and stratified estuary
using high frequency transducers (120kHz) on tripods placed across the main channel
of the river flow. The measurements are taken in the Connecticut River across several
tidal cycles, when the flood tide causes a wedge of seawater to press up the river
bed, beneath the fresh water, and then be eroded and pushed back out during the
ebb. BELLHOP, implemented via Matlab, is a beam/ray tracing method and is used to
model the acoustic propagation in this environment using collected temperature, salinity,
and depth data. Multiple modeling comparisons are done over the period of three
full tidal cycles, totaling a thousand separate modeling runs and compiled into a time
series. Arrival times measurements from the transducer system were able to be accurately
modeled, validating BELLHOP as a useful tool in modeling this very dynamic and
challenging acoustic environment.