An experimental study of the effects of resilient bars on plate vibration

Resilient bars can provide a low-cost, effective improvement to sound insulation performance. They are commonly used in timber-framed floor/ceiling assemblies in North America and Europe. Resilient bars are often modelled as springs isolating the two connected plates thereby forming a mass-spring-mass system. However, as a furring system of plates, resilient bars may modify the vibration energy distribution across a connected plate by acting as stiffeners. The authors investigate this issue by measuring acceleration levels at different locations relative to the fixing positions and thereby derive vibration waveforms for the connected plate in a small-scale structural simulation of a floor-ceiling system. The results were compared with timber-joist-ribbed, and timber-brander-ribbed, structures. The vibration modes of a suspended plate were also measured for comparative purposes. The results indicated that resilient bars did not perform as stiffeners whereas joists and timber branders did effectively stiffen their connected plates. Resilient bars neither forced orthotropic plate behaviour at low frequencies, nor separated the plate into sub-plates at higher frequencies. Resilient-bar-ribbed plates may also differ from independent plates. The modal behaviour of resilient-bar-ribbed plates is more complex and their effect on modal density and radiation efficiency are worthy of further research.