MULTIPLE-SCATTERING OF ULTRASOUND IN SUSPENSIONS

Measurements of ultrasonic velocity and attenuation on a suspension of sub-millimetre polystyrene spheres in a solution of aqueous sodium ch loride were carried out over a frequency range of 4-12 MHz, for solid volume fractions varying between 0 and 0.5. A method of predicting the volume fraction at which the single scattering approximation becomes unphysical due to multiple scattering has been proposed for these meas urements. A comparison of the experimental data with the theoretical p redictions of single scattering and two multiple scattering approaches has been made. Good agreement was obtained between the experimental a nd theoretical approaches, the predictions of the iterative multiple s cattering model most closely approximating the experimental results.