A simulation based study of low frequency transient sound radiation from floors : a concrete vs. a hybrid floor

Timber is a renewable and human friendly construction material and thereby a potential solution toachieve life cycle sustainable buildings. However, it is clear that impact sound and vibrations withinthe low frequency range still are challenges for wooden joist floors. Another challenge is the,mostly, larger building heights of wooden or hybrid floors compared to the heights of concretefloors. Using timber as the structural joist floor material could imply fewer stories due to maximumallowed building heights, which renders in less income in a building project. Accurate simulationsof impact sound may decrease the need for prototypes; thus saving money and time in the timberbuilding industry. Here, a hybrid joist floor consisting of wood, sand and steel is compared to aconcrete floor in terms of radiated impact sound into a rectangular cavity. The hybrid floor is designedsuch that its mass distribution and global stiffness are close to the same properties of theconcrete floor. Finite element models are used for simulations of the radiated transient sound inducedby impact forces having the characteristics of human walking. The simulations indicate thatsimilar surface mass and bending stiffness of a floor intersection give similar impact sound transmissionproperties around the first bending mode, while it is not necessary so at higher frequencies.Keywords: timber buildings, impact sound, simulatio