title: Acoustic waves in an elastic channel near the free surface of granular media.
abstract: A theoretical description of a natural acoustical waveguide existing in unconsolidated granular materials due to a gravity-induced stiffness gradient is proposed. The analytical theory for the acoustic modes propagating in the medium with a power-law type inhomogeneity uses some original solutions of the Helmholtz equation that have not been derived before either in classical or in quantum mechanics. The dispersion relations and a physical mechanism of localization for these modes indicate their essential difference both from the Rayleigh surface acoustic waves and the waveguide modes in homogeneous plates.
authors.affiliation: Laboratoire de Physique de l'Etat Condensé UMR-CNRS 6087, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans cedex 9, France.
authors.forename: V E
authors.initials: VE
authors.lastname: Gusev
authors.forename: V
authors.initials: V
authors.lastname: Aleshin
authors.forename: V
authors.initials: V
authors.lastname: Tournat