Modeling acoustic scattering from the seabed using transport theory

Radiative Transfer (RT) theory has established itself as an important tool for electromagnetic remote sensing in parallel plane geometries with random distributions of scatterers, and most recently it has also been proposed as a model for the propagation of elastic waves in layered ocean sediments. In this work the capabilities of this model are illustrated, as the RT method is used to predict backscattering strength from laboratory models of random media. The RT model is characterized by its flexibility on accommodating scatterers in a broad variety of sizes, shapes, and acoustic contrast relative to the background media. Additionally, this formulation is easily expandable to include multiple layering and elastic effects. In this paper, a comparison between the RT model and the results from two laboratory experiments in the optics and the Mie regime are presented. The experiments were designed to measure volume scattering at high frequencies between 280 kHz and 400 kHz in monostatic configuration. The first experiment used large aluminum spheres suspended with thin filaments, and it serves as a benchmark for testing the RT formulation due to its high signal-to-noise ratio, and the absence of reflective boundaries or background attenuation. Measurements of frequency dependent backscattering at normal incidence angle are shown for two fractional volumes. For the second experiment, the scattering media is a well characterized slab of a lossy resin background containing a uniform distribution of glass beads, and angle- and frequency-dependent measurements are presented. The levels of volume scattering from both experiments are found in agreement with predictions from the steady state RT model.