Numerical results for ……. show that with a 5% error in the frequency ….(which is typical for engineering problems) the string model is approximately valid for ….. the beam model for ….. and the stretched beam model for …... Application of the beam model is of course also restricted by the 3D theory of elasticity, that is, additionally it should be assumed that …. and …... From now on it will be assumed that for …. the string model can be used, that for…… the stretched beam model can be applied, and that for …. the beam model can be used. In this paper it will be assumed that the solutions of the separate models are not interacting. In the next two sections the behavior of the string model and the beam model will be discussed, because these (partly) truncated models have not yet been treated in the literature.