Scattering and Reverberation Uncertainty in Shallow Water Environments due to Environmental Variability

Abstract

Award Number: N0001403WX20830 http://www.nrl.navy.mil LONG-TERM GOALSTo quantify sonar uncertainty in the common tactical environmental picture. As a member of the seafloor uncertainty team quantify the effects of seafloor uncertainty on propagation, scattering and reverberation. OBJECTIVESPropagate uncertainty in the background and statistical properties of the bottom through to corresponding measures of the uncertainty of scattering strength, propagation and reverberation. APPROACHWorking closely with the geophysicists, hydrographers and experimental geoacousticians on the seafloor uncertainty team, obtain and propagate quantitative estimates of bottom parameter uncertainty through to propagation, scattering and reverberation uncertainty using high fidelity time domain models developed at SACLANTCEN and NRL. Statistical realizations of heterogeneous seafloor sound speed are provided by John Goff (UTIG), with input on sediment surficial sound speeds measured by Barbara Craft and Larry Mayer (UNH). Bottom scatter strength and reflection measurements and associated uncertainty are provided by Charles Holland (ARL/PSU). WORK COMPLETEDIn the FY02, a statistical method for predicting the uncertainty of shallow water waveguide propagation under the adiabatic approximation in the frequency domain [1] was extended to treat uncertainty in time domain propagation and reverberation [3,4] using the narrowband approximation.Estimates of reverberation uncertainty were built upon a coherent model for reverberation developed at SACLANTCEN [2]. The results showed that bottom uncertainty induced uncertainty most strongly in the late time multipath arrivals, whereas oceanographic uncertainty most strongly affected axially propagating earlier arrivals.In FY03 the qualitative behaviors seen in the adiabatic predictions during FY02 were confirmed using fully coupled models for propagation ) and reverberation ). In addition, the volume scattering extension to OASES was reported this year and this tool was used to predict the 1