22. Influence of Furniture on the Modal Properties of Wooden Floors

Structure-borne vibration and low-frequency re-radiated noise from internal and external sources cause annoyance for inhabitants in dwellings. A key parameter in the prediction of vibration and noise levels is the modal parameters of the floors in a building, since vibration and sound levels increase when natural frequencies of the floor coincide with the excitation frequencies of a source, e.g. monoharmonic vibration of unbalanced rotating machinery and appliances or HVAC system—or traffic induced ground vibration propagating into the building. This paper has focus on wooden floors built as an assembly of particleboard and timber joists. Such floors constitute horizontal divisions in many dwellings—both older, traditional buildings and new lightweight buildings. The analysis concerns the impact of furniture placed on a floor with otherwise known properties. Given the small mass of a traditional wooden floor, the presence of furniture can be expected to change the modal properties of the floor significantly. The finite-element model, developed for the present analyses, accounts for uncertainty in the position of the furniture, and the analysis addresses the importance of the elevation of the mass above the floor regarding the natural frequencies and the related modes of vibration.