Measurement of the Biot Structural Factor δ: for Sintered Bronze Spheres

We have extracted the Biot structural factor 6 [11 for three samples of sintered bronze spheres (nom. dia. 7511, 11011, 50011, porosity 0.4 to 0.5) from measurements of the speed and attenuation of first and second sound in superfluid helium contained in these samples. We find 1 to lie in the range 3.3 to 4.5, about 1+ to 2 times larger than Stoll has estimated for typical marine sediments 121 (we take 6 to be defined by x=6 (awk/vP)', where is the argument of Biot's universal correction function F(K), a is the tortuosity, is the angular frequency, k is the permeability, v is the kinematic viscosity, and P is the porosity). If 6 is the normalfluid viscous p&&ration depth and a is a characteristic pore size, the range of /a covered by these measurements is ximately 0.01 to 1.