Finite element simulations of sound insulation are very problematic due to problem of damping. Omitting damping issues in dynamic analysis, which in conclusions leads to acoustic performance of system may reflect in non-reliable results. In this paper study using different values of Rayleigh damping coefficients are used for Explicit analysis to calculate structural reverberation time. To investigate behaviour of structure under different damping the structural reverberation time and the total loss factor is calculated. The modelled slab was 14 [cm] thick and geometry of considered plate is 4.19 x 3.61 [m]. Load on the structure was applied in 3 different points with unit pressure on small area (5x5 [cm]) using amplitude of load as Dirac delta approximation. Results of performed simulations of the slab subjected to impact load were compared with laboratory result of structural reverberation time measurements obtained with accelerometers. As a result of this analysis it can be stated that damping is crucial issue to reflect acoustical behaviour of considered structure. Results shown that β-coefficient of Rayleigh damping affects more structural response than α-coefficient especially in medium and high frequency. Comparing simulation results with laboratory measurements and formulas to calculate α- and β-coefficient of Rayleigh damping it can be concluded that formulas used in structural dynamics for estimating damping coefficients in simulation of whole building are not valid for simulation of individual building elements. These formulas can be used only for initial estimation of damping coefficients. In considered situation gave effect of over dampening tested slab. Based on this conclusion additional simulations were performed to conclude that β-coefficient is overestimated by order of magnitude.