Among the several parameters involved in rock fall analisys, therestitution coefficient, which is related to the kinetic energy wasted after repeated impacts of a rocky body against the ground, is probably the most important and most difficult to acquire. There is the necessity of in situ tests where blocks of rocks are thrown down on the slopes. However these tests cannot be performed in places where people or urban equipments could be in risk. In this paper anacoustic method is used for the measurement of the normal restitution coefficient of rocks. This method is very well known by physicists but it has not been applied in the geosciences and engineering areas. It consists in the sound recording of successive impacts of a rock sphere against a smooth rocky surface.The gravity acceleration was back calculated from data obtained in order to verify if precision of the method is suitable. A sensibility analysis of the coefficient of restitution was already carried out simulating real rock fall problems.