We study a problem of wave propagation in a structure made of two tridimensional elastic bodies connected by a thin adhesive layer. We recall that, after several heuristic models, the bonding problem, which basically amounts to study how does the thin layer can be replaced by a simpler model without thickness, has been carried out in the case of equilibrium problems. The present work deals with the dynamical problem. We obtain that the problem of elastodynamics with a thin adhesive layer can be approximated, with a convergence result, by another problem in which the layer is changed into a mechanical constraint, which is precisely the same as the one of the equilibrium case.