Impacted lightweight stairs as structure-borne sound sources

The requirements and methods of characterising impacted lightweight stairs as sources of structure-borne sound and of predicting the resultant sound pressure in buildings are described. The approach is to treat the stair system and the excitation as a single active source. In this study, the stair is excited by a tapping machine or an instrumented shaker, although the approach lends itself to the use of walkers ascending and descending the stair. The approach provides laboratory data suitable for prediction of the structure-borne power transmission from the stair to the supporting wall in a building and thence the resultant sound pressure in adjacent spaces. For the case studied, the primary transmission path is through a bolt to a supporting wall, which also is the separating wall between dwellings. This is a common situation in Germany. The source data can be the velocity of the free source at the contact point and the associated point mobility. Alternatively, a reception plate method is considered, which yields the source power. The approaches provide laboratory data appropriate for prediction of the resultant sound pressure in adjacent rooms using existing building propagation models. By comparison of predicted and measured sound pressure levels, the achievable accuracy is assessed and sources of uncertainty are highlighted.