Sound waves in foams

A new (film) model is proposed for the propagation of sound waves in gas–liquid foams. The model explains the effect of sound retardation in foams by foam films inertness. It qualitatively agrees with the experimental data on the velocity of sound propagation in foams of various structures. The high absorption of sound in foams is explained by hydrodynamic losses in foam films. The experimental dependence of the sound absorption coefficient on the foam expansion is explained. The calculated expansion corresponding to the absorption maximum is close to the experimental value.