Acoustic attenuation due to bi-modal size distributions of suspended sediment

Abstract

Hanes, D.M., 2016. Acoustic attenuation due to bi-modal size distributions of suspended sediment. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 23 - 27. Coconut Creek (Florida), ISSN 0749-0208.Acoustic backscatter is a technique commonly used to remotely measure the concentration profile of suspended sediment. The technique generally involves an inversion, because the backscattered sound intensity depends upon the range dependent concentration and size distribution of the sound-scattering particles. This work examines the attenuation of sound due to particles, and in particular evaluates the relative contributions of viscous attenuation verses scattering attenuation as a function of the size of the particles. It is found that under some conditions viscous attenuation is dominated by smaller sized sediment and scattering attenuation is dominated by larger size sediment, but this result is not true in general, and depends upon the particular particle size distribution.