Acoustic predictions of the recently developed TRACEO ray model, which accounts for bottom shear properties, are benchmarked against tank experimental data from the EPEE-1 and EPEE-2 (Elastic Parabolic Equation Experiment) experiments. Both experiments are representative of signal propagation in a Pekeris-like shallow-water waveguide over a non-flat isotropic elastic bottom, where significant interaction of the signal with the bottom can be expected. The benchmarks show, in particular, that the ray model can be as accurate as a parabolic approximation model benchmarked in similar conditions. The results of benchmarking are important, on one side, as a preliminary experimental validation of the model and, on the other side, demonstrates the reliability of the ray approach for seismo-acoustic applications.
Following the derivation presented by Press and Ewing [Geophysics 15, 426–446 (1950)], a normal mode solution for the Pekeris waveguide problem with an elastic bottom is outlined. The analytic solution is benchmarked against data collected in an experiment performed at the Naval Research Laboratory [Collis et al., J. Acoust. Soc. Am. 122, 1987–1993 (2007)]. Comparisons reveal a close match between the analytic solution and experimental data. Results are strongly dependent on the accuracy of the horizontal wavenumbers for the modes, and horizontal wavenumber spectra are compared against those from the experimental data.
Vector Sensor Arrays (hereafter VSAs) are progressively becoming more and more attractive among the underwater acoustics community due to the advantages of VSAs over standard arrays of acoustic hydrophones. While the later record only acoustic pressure, VSAs record also particle velocity; such technical feature increases by a factor of four the amount of information that can be used for the processing ofacoustic data, leading to a substantial increase in performance. Since VSA sensor technology is relatively recent, and thus not yet fully available, one can consider the usage of closely located pairs of standard hydrophones, which can be used to estimate the vertical component of particle velocity as a difference of acoustic pressure, measured at each pair of hydrophones. The present discussion introduces a theoretical review of particle velocity calculations using different acoustic models, and tests the performance of estimators for geoacoustic inversion using acoustic pressure, particle velocity components and direct and approximated values of the vertical component only.
Acoustic scattering from a rough sea surface in propagation modeling is generally treated using a single-scatter approximation in which only specular components are considered and the incoherent field is neglected. This work presents energy-flux calculations of transmission loss for a shallow water waveguide with a rough sea-surface following a Pierson-Moskowitz spectrum. Multiple scattering is evoked by considering conservation of energy from scattering events. Comparisons are made between the model with multiple scattering and that using the single-scatter approximation. Models are compared to the direct solution using the boundary element method. [This work was partially funded by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program, the Eric Walker Fellowship from the Applied Research Laboratory at the Pennsylvania State University, and the Achievement Rewards for College Scientists (ARCS) Foundation Pittsburgh Chapter.]
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