Measurements and predictions of the phase velocity and attenuation coefficient in suspensions of elastic microspheres

The phase velocities and attenuation coefficients for suspensions of narrow ly sized polymer microspheres are reported over a broadband spectrum from 3 to 30 MHz. The six suspensions used in this work contain microspheres with respective average diameters near 40 mu m, 50 mu m, 60 mu m, 70 mu m, 80 m u m, and 100 mu m. The results of these measurements are compared with theo retical expressions for the phase velocity and attenuation coefficient deri ved from the scattering properties of an elastic sphere in water using the weak scattering limit of the Waterman and Truell dispersion relation [J. Ma th. Phys. 2, 512-537 (1961)]. This single-scattering limit of the theory is found to be sufficient for predicting the ultrasonic transport properties of these suspensions to a considerable degree of accuracy. (C) 1999 Acousti cal Society of A,America. [S0001-4966(99)05608-8].