Simulations of outdoor sound propagation using a time-domain approach have proved to be efficient to deal with complex situations. Indeed, the main effects on acoustic propagation can be taken into account. In particular, recent works [Dragna et al., AIAA J. 49, 1420-1428 (2011); Dragna et al., AIAA-Paper 2010-3758 (2010)] have shown that impedance of the ground surfaces and topography can be modeled efficiently in time domain. In this paper, results from an experimental campaign carried out near a railway high speed line in 2010 are compared to those obtained with a finite-difference time-domain (FDTD) solver of the linearized Euler equations. During the experiments, the topography of the site and the different surface impedances have been determined. Meteorological measurements have also been performed. A blank pistol is used to obtain impulsive signals. The different measured parameters are used as input data into the FDTD solver. Comparisons are realized in both the frequency domain, and in the time domain.