Measurements of scattering by suspensions of irregularly shaped sand particles and comparison with a single parameter modified sphere model

Measurements are presented of multi-frequency underwater acoustic backscattering from suspensions of glass spheres and sands. The data were collected in a sediment tower, specifically designed for such measurements and capable of generating a homogeneous suspension over a distance of approximately 1 m. The glass sphere data were collected to assess the capability of the system and for calibration. The measurements on suspensions of sands were obtained as part of on-going studies into the measurement of nearbed sediment transport processes using acoustics. Utilizing the backscattered sound from sand suspensions, both the form function and total scattering cross section of the sediments have been measured for a range of sediments and particle sizes. Interpretation of the observations has been carried out within a framework of sphere scattering. The results show enhanced scattering for suspensions of sand grains, relative to that of similar size spherical scatterers and the enhancement can be described by a function dependent on the particle size and the wave number of the insonifying sound, with one free parameter. (C) 2004 Acoustical Society of America.