Sound speed in air-filled sands and marine shallow-layer sediments (sands)

Based on the author's theory for acoustic propagation in granular media and employing the extinction theorem, the sound speed formulae in these media are given. The numerical computations for sound speed in marine sediments and air-filled sands are carried out, the results of which demonstrate that under the normal atmosphere the sound speed in air-filled sands is lower than the sound speed in the air, The numerical results also demonstrate that the influence of scattering interaction between the grains upon the sound speed in the marine shallow-layer sediments (sands) has to be taken into account; however, the interaction of viscous waves can be neglected. The theoretical results obtained from the rigid-granular model seem to match the measured data better than from the elastic-granular model, even the latter model is fitter for the real situation, which means that still more further measurements will be necessary in order to gain an insight into this problem. Through an analysis of experimental data published in journals a conclusion can be drawn that the theory of granular media is suited better than the theory of porous media to deal with the problems of the sound propagation in air-filled sands.