CAN SOUND BE LOCALIZED IN GRANULAR MEDIA

Liu and Nagel have reported recently [Phys. Rev. Lett. 68 (1992) 2301 ] a set of measurements involving sound propagation in an unconsolidat ed granular glass beads system (an artificial ''sand''). In order to r ationalize qualitatively and quantitatively the reported results, we p ropose the physical picture that sound waves are multiply scattered at grain-grain contacts and are thus in the diffusive regime, close to A nderson localization. This suggests a deep link between the quest for experimental observation of strong localization for classical waves an d the physics of unconsolidated granular media.