Dissipative properties of vibrated granular materials

We investigate collective dissipative properties of vibrated granular mater ials by means of molecular-dynamics simulations. Rates of energy losses ind icate three different regimes or "phases" in the amplitude-frequency plane of the external forcing, namely solid, convective, and,gaslike regimes. The behavior of effective damping decrement in the solid regime is glassy. Pra ctical applications are discussed.