Ultrasonic velocity dispersion in porous materials

Abstract

An analytic expression for the ultrasonic dispersion in porous materials is obtained. It is shown that size determination of pores of a few microns radius using ultrasonic dispersion should be possible with available techniques. For pores with radius 0.1-1 mu m higher frequencies, such as those characteristic of vapour-deposited transducers, will be necessary. The velocity dispersion and ultrasonic attenuation depend on averages of different powers of the pore radius. A measurement of both will give information on the mean square deviation in pore sizes as well as the average pore size.