The mechanisms responsible for the transmission of sound in building elements such as floor/ceiling systems are complex and not yet fully understood. In an attempt to understand some of these phenomena, an analytical model was developed for finite and non-periodical floor/ceiling systems to predict their low frequency response to impact excitations. The finite dimensions of the structure are taken into consideration by adopting a modal approach whereby the displacements and pressure fields are expanded into infinite series of admissible functions. The solution relies neither on the periodicity of the stiffened ceiling panels or suspension system nor on the infinite extend of the floor. The paper presents briefly the modelling approach leading to the prediction of the quadratic vibration velocity of the ceiling panel. Finally, comparisons are made between measurements and prediction.