© The authors and ICE Publishing: All rights reserved, 2015.Numerical analyses of induced ground vibrations play an important role in assessing building safety and comfort. One of the major difficulties is related to the calibration of an adequate source model to be used in the numerical simulation. In this paper the attenuation of waves caused by drop load tests is considered to provide a general framework for the evaluation of vibration attenuation both with empirical laws and numerical simulations. A new equation to reproduce the source signal is suggested and used as input for a dynamic coupled consolidation Finite Element Analysis. The model is validated through comparison with field data obtained at a site in the vicinity of the Tower of Pisa, Italy, from geophones at various distances from the impact source. The calibrated numerical model is then used to study in detail the attenuation of waves from the source and assess the validity of empirical attenuation laws.