Sound damping in frictionless granular materials: The interplay between configurational disorder and inelasticity
We numerically investigate sound damping in a model of granular materials in two dimensions. We simulate evolution of standing waves in disordered frictionless disks and analyze their damped oscillations by velocity autocorrelation functions and power spectra. We control the strength of inelastic interactions between the disks in contact to examine the effect of energy dissipation on sound characteristics of disordered systems. Increasing the strength of inelastic interactions, we find that (i) sound softening vanishes and (ii) sound attenuation due to configurational disorder, i.e. the Rayleigh scattering at low frequencies and disorder-induced broadening at high frequencies, is completely dominated by the energy dissipation. Our findings suggest that sound damping in granular media is determined by the interplay between elastic heterogeneities and inelastic interactions.