What does multiple scattering tell us about rheology?

Longitudinal viscosity can be obtained at all frequencies directly from measurements of ultrasound/acoustic attenuation and sound velocity. The bulk viscosity can then be obtained from the longitudinal viscosity provided a measure of the shear viscosity is available. Unfortunately, the shear viscosity values chosen may be entirely inappropriate because the viscosity experienced by an oscillating particle need not be the same as that determined by low frequency oscillatory rheology. The relationships between acoustical/ultrasound parameters such as attenuation and sound velocity, bulk and shear viscosity will be presented and the role of multiple scattering in these measurements discussed. The use of dispersed phase particles, visco-inertial scattering and multiple scattering will then be considered as a possible way of determining high frequency shear viscosity.