Numerical and experimental studies have been undertaken to analyze the compaction of a granular media submitted to sinusoidal horizontal vibrations. We characterize especially the influence of the dimensionless acceleration Γ of the vibrations and of the size of the box. For low value of Γ, the surface layers are compacted and the bottom layers remain at their initial density. The jamming effect of the bottom layers is explained by the influence of the pressure in these layers, which constraints the grains in their displacements. For high values of Γ, the bottom layers get compacted, the surface layers are fluidized and the density is decreased. We have also noticed that the compaction intensity depends on the size of the box: when the size of the box is lowered, the compaction becomes smaller.