Molecular dynamics simulations have been carried out on a two-dimensio
nal model granular material made up of inelastically colliding discs s
ubjected to gravity. The granular system is fluidized by a constant en
ergy input from a vibrating base, and a stationary non-equilibrium sta
te is achieved. Density and granular temperature profiles are determin
ed, while the former goes through a maximum at intermediate altitudes,
the latter exhibits a minimum at a higher altitude, beyond which the
granular temperature is found to increase. Local density fluctuations
are characterized by the time-displaced density autocorrelation functi
on. Longitudinal compression (sound) waves propagating in the horizont
al direction are found to be strongly damped, while they are overdampe
d in the vertical direction at the longest accessible wavelength.