Surface-wave modes on soft gels

To understand behavior of surface waves on sols and gels, the dispersion re lation of surface modes on isotropic materials with both surface tension an d elasticity is studied. The dispersion relation consists of two separate b ranches: one corresponds to the truly localized Rayleigh-type modes which c an exist only at low frequencies, while the other, which is connected conti nuously to the capillary modes, gives pseudo-surface waves that are damped, radiating elastic transverse waves into the bulk of the medium just like t he ones known in surface waves on elastically anisotropic materials. The re sult is compared with recent experiments on sols and gels. (C) 1998 Acousti cal Society of America. [S0001-4966(98)04312-4].