PROBING POROUS-MEDIA WITH 1ST AND 2ND SOUND .2. ACOUSTIC PROPERTIES OF WATER-SATURATED POROUS-MEDIA

The ultrasonic properties (reflection/transmission and bulk attenuatio n/speed) of porous and permeable media saturated with a Newtonian flui d, namely water, are considered. The frequency dependence of the trans mission amplitudes of pulses is measured through a slab of thickness d 1, repeated for another slab of thickness d2 for a given material. Wit h these two measurements on two different thicknesses, it is possible in principle to separate bulk losses from reflection/transmission loss es for compressional waves in these materials. The bulk properties are calculated from the Biot theory for which all of the input parameters have been measured separately; the attenuations are particularly sens itive to the values of LAMBDA, determined from second-sound attenuatio n measurements reported in the companion article. There is excellent q uantitative agreement between the theoretical and experimental values in the cases considered; there are no adjustable parameters involved. The reflection and transmission coefficients are reported for some of the multiply reflected pulses and their amplitudes are compared with t hose calculated from the Deresiewicz-Skalak and Rosenbaum boundary con ditions appropriate to either the open-pore or sealed-pore surfaces, a s the case may be. Again, there is excellent quantitative agreement be tween theory and experiment. Compared with the open-pore boundary cond itions, it is noted that there is a large reduction, both theoreticall y and experimentally, in the efficiency with which the slow compressio nal wave is generated when the sealed-pore boundary conditions apply, but this efficiency is not reduced to zero.