Acoustic phenomena in porous media studied by transient grating spectroscopy: A critical test of the Biot theory

Acoustic-wave propagation in liquid-filled porous glasses has been studied by a heterodyne detected transient grating experiment. A test of the Biot theory is presented under two new regimes, namely, for a new frequency range up to 1.3 GHz and for porous media with nanometric scale heterogeneities. We show that the Biot theory describes the sound velocity data correctly, but does not account for the acoustic attenuation. We suggest that the acoustic damping is mainly due to the dissipation mechanisms intrinsic of the matrix and the liquid which are not accounted for in the theory.