Flanking transmission of lightweight floors
New building systems are often lightweight in character, with wooden or thin-walled metal joists. An often-noticed weakness in these types of constructions is the poor sound insulation. Without an acceptable sound insulation, these building systems cannot be used in practice. One of the difficulties when designing the system is to handle the flanking transmission, i.e., when the sound passes through the structure in other paths than the direct one (via junctions). In connection to lightweight building techniques, the junctions can be designed in a number of ways, and it is therefore important to have the theoretical tool to predict the structure borne sound transmission loss of the junctions. Measurements, that are expensive to perform, can then be made on the design alternatives that seem most promising. The existing prediction methods often used in building acoustics are not well suited for lightweight structures; they cannot handle periodicity. In this project a novel predication model is therefore under development. The prediction model will be able to handle details in the building structure, but also able to handle uncertainties in the material and geometrical properties of the structure.
Qualification of the sound diffusion in rooms
The aim of this project is to develop a laboratory method for measuring the diffusing effect of non-absorbent objects in rooms with ceiling absorbers. The diffusing effect is quantified in a measure called equivalent scattering absorption area Asc.