Airborne sound insulation of single-leaf partitions under hygric load

Abstract

In buildings of all types the use of single-leaf partitions are recommended, not least for reasons of cost efficiency and possible resource optimisation. In addition to the familiar building physics topics they play also a particularly important role in noise protection. Numerous factors influence the acoustic properties of single-leaf, plate-shaped and dry partitions. These include the mass, the bending stiffness, the position of the critical frequency and the total loss factor of the partition as well as the stimulating frequency of the airborne sound, the sound incidence angle or the characteristic impedance of the air. Each mineral wall-building material has its own product-specific pore structure. In the usual calculation of the airborne sound insulation of single-leaf, airtight and dry partitions, this has so far not been taken into account. It is precisely in these building material pores that a hygrothermal, continuous adjustment of the moisture content takes place in addition to the production-related water quantities. This changes the mass of the building component and thus the airborne sound insulation of the wall. In addition to this well-known mass effect, a further mechanism, which has not yet been considered, increases airborne sound insulation: the smaller the pore sizes in the building material, the greater the mechanical forces caused by stored pore water. The existing equations for airborne sound insulation do not take these effective forces into account and must therefore be extended. The wall building material is considered as a porous medium with solid and fluid components. The new calculation approach allows the calculation of the airborne sound reduction index for single-leaf partitions under hygric load for saturated and partially saturated moisture conditions with high accuracy. The calculation results provide valuable information for the planning and product development of new building materials.