The Spectral analysis of Surface Waves SASW allows to determine the speed profile of the shear waves of a particular ground. The method is based on the use of the dispersive properties of surface waves (Rayleigh) generated by a surface impulsive input. The depths explored vary from a few centimetres (road floors) to a few tens of metres. SASW is carried out by placing 2 geophones in line, in the ground, with oscillation frequency from 14 to 1 Hz, and registering the seismograms. The speeds profile of waves Vs is obtained from studying the phase speeds of Rayleigh waves. The data elaboration consists in determining the Coherence function, the Cross Power Spectrum phase and the construction of the dispersion curves of the Speed during the experimental phase in depth. In conclusion, the propagation phenomenon of the surface waves is simulated with the purpose to identify the rigidity profile reproduced by the experimental dispersion curve.