A review of the scattering properties of suspended sandy sediments for the application of acoustics to sediment transport studies

Multi-frequency acoustics backscattering has been used for over a decade, to quantitatively measure, in the marine environment, near-bed profiles of suspended sediment particle size and concentration. Central to obtaining the sediment parameters from the backscattered signal, is a description of the scattering properties of irregularly shaped particles randomly distributed in space. Formulations are therefore required for both the attenuation and backscattering properties of suspensions of sedimentary particles with size and acoustic frequency. There is no rigorous analytical solution or single formulation for these scattering properties and different researchers have used somewhat different expressions. Here we bring together four decades of published data on the acoustic scattering properties of suspensions of sandy sediments. These data are reformulated in terms of the usual acoustic scattering nomenclature, that is the form function and the normalised total scattering cross-section and simple heuristic generic expressions, based on a sphere scattering model, are formulated to describe the sediment scattering properties. The expressions are not limited to sand particles, but should have broad applicability to irregularly shaped particle scattering.