ICSV22, Florence (Italy) 12-16 July 2015 1 THE EFFECT OF DAMPING IN RESILIENT MATERIALS USED IN FLOATING FLOORS ON IMPACT SOUND INSULA- TION Alessandro Schiavi and Andrea Prato INRiM – National Institute of Metrological Research, str. Delle Cacce, 91, 10135 Torino, Italy e-mail: a.schiavi@inrim.it Luca Barbaresi and Giovanni Semprini DIN Dipartimento di Ingegneria, Università di Bologna, via Risorgimento 2, 40136 Bologna, Italy Resilient materials are nowadays widely used as underlayers in floating floors, in order to reduce the transmitted impact sound pressure level. A floating floor, i.e. a floating slab on a resilient support applied on the structural base floor, behaves as a classical mass-spring- damping system and its motion is analytically described in terms of the Newton’s second law. As a consequence, because of the resilient nature of the supports, the coupling of the vi- bration field of the floating slab to the structural base floor depends both on the resonance frequency and dissipative effects. As shown in this paper, the internal damping of resilient materials plays a role in insulation of impact sound, by varying the slope of the attenuation curves. As a matter of fact, the spectral distribution of energy transmitted through a mass- spring-damping system strongly depends on elasticity close to the resonance frequency of the system, but depends also on damping at higher frequencies. 1. Introduction Structural sound transmission and vibration in dwellings is one of the most relevant problems in building acoustics. The main causes are footfall noise, and any friction or percussion effects (e.g. chairs dragging, equipment working, electrical domestic appliances). The propagated sound radiates in rooms even far from the source. The use of resilient materials decoupling structures in floors al- lows controlling and reducing the transmitted vibrations at source. Floating floor is one of the most effective building technologies as a protection against impact sound and vibration propagation in structures and a wide resilient underlayer assortment is commercially available: mineral and syn- thetic wools, synthetic felts, polyurethane foams or other polymeric compound and various recy- cling materials as tyre shavings, wood tailings, cork and natural wool waste. In general terms a floating floor, consists in a rigid and low damped floating mass (commonly concrete or lightweight concrete ~ 60/120 kg/m 2 ), uncoupled from the structural base floor, by means of a continuous resil- ient layer. This can be described as a mass-spring-damping system. The assessment of the reduction in impact sound pressure level L of a floating floor system is evaluated in laboratory according to the International Standard series ISO 10140. A standard test