The Effect of Mechanical Connectors on the Sound Insulation of Structural Insulating Panels

Structural insulating wall or roof panels integrate the required thermal insulation with the mechanical performance in one sandwich element, consisting of a foam core between structural skins. The combination of low mass and high stiffness typically results in a lower sound insulation over a large frequency band. Furthermore, the presence of mechanical connectors between both skins, necessary for structural or fire-safety reasons, can alter the performance. This paper investigates the effect of point connections on the sound insulation by means of experiments and two modelling approaches. The first one integrates correction terms for the connectors in the transfer matrix method (TMM) framework. The second one extends the hybrid wave based - transfer matrix method (WB-TMM), which was previously developed for modelling finite-sized sandwich panels. The TMM predicts a significant decrease in the transmission loss at higher frequencies due to the presence of mechanical connectors. The WB-TMM only predicts a slight decrease in the transmission loss at high frequencies. The transmission loss around the mass-spring-mass resonance dip at mid frequencies even increases because the mechanical connectors restrict the vibration of the skins at resonance. Laboratory measurements of the sound insulation of structural insulating panels with and without mechanical connectors confirm these findings.