An effective density fluid model for acoustic propagation in sediments derived from Biot theory

In this paper we present an acoustic propagation model that approximates a porous medium as a fluid with a bulk modulus and effective density derived from Biot theory. Within the framework of Biot theory it is assumed here that the porous medium has low values of frame bulk and shear moduli relative to the other moduli of the medium and these low values are approximated as zero. This leads to an effective density fluid model. It is shown that, for saturated sand sediments, the dispersion, transmission, reflection, and in-water backscattering predicted with this effective density fluid model are in close agreement with the predictions of Biot theory. In this agreement we demonstrate that the frame bulk and shear moduli play only a minor role in determining several aspects of sand acoustics. Thus, for many applications the effective density fluid model is an accurate alternative to full Biot theory and is much simpler to implement. (C) 2001 Acoustical Society of America.