BUILDING PHYSICS 6 SOUND INSULATION Sound insulation serves the purpose of protecting people adequately from noise in social rooms. In timber construction, the components always comprise multiple layers. This way, the sound encounters multiple resistances on its path in between the individual components. While the sound insulation of single-layer components is based exclusively on their mass and flexural stiffness, smart multi-layer structures with decoupled layers and hollow space insulating materials can reach steady sound insulating values with substantially lesser masses. The construction situation is decisive for the evaluation of sound insulation. This means that given the requirements of sound insulation, a separating component must always be evaluated including the secondary sound paths. binderholz CLT BBS In solid timber structures, foremost the total thickness of the cross laminated timber CLT BBS, its surface weight and flexural stiffness play an essential role for the sound insulation of the basic component (without further layers). Generally, the complete component (wall, ceiling, roof) is supplemented by additional layers (façade, installation level, floor structure, etc.) The sound insulation of the complete component is significantly improved by additional cladding. Components made of CLT BBS are made of modular elements. The modular connections required due to the structure are tested comprehensively for sound insulation and designed so that they do not have any negative effects on the indicated sound insulation value. For the use of CLT BBS as separating ceiling or partition wall in a residential unit, component assemblies have been developed in the course of comprehensive testing at the ift Rosenheim that meet the relevant requirements for sound insulation. The measuring results illustrate clearly that these optimised assemblies also withstand comparisons to reinforced concrete walls and notably so with one-fifth of the mass. Rigips dry construction systems Layers with large surface measures, for example, plasterboards have a positive effect on sound insulation. By additionally mounting an installation level, a flexible shell is created that substantially increases sound insulation in high and medium frequency ranges. Here, flexible bearing profiles such as RigiProfil as well as heavy flexible panelling, e.g. Rigips fire protection plates should be used and the largest possible shell spacing should be ensured. Air-borne sound insulation A structure is excited to oscillate during sound transmission. In the case of multi-layer structures, the insulating material in the hollow space affects the coupling of the individual layers and the sound distribution inside of the hollow space. The rated sound insulation value R’w [dB] indicates the sound insulation of a component between two rooms including secondary sound paths (see Figure 1). The sound insulation of multi-layer components depends on the characteristics of each individual layer and on the interaction of all layers. The properties of the individual layers depend on their surface measure (mass inertia) and flexural stiffness. For example, the sound insulation can be improved by mounting an installation level in addition, which consists of plasterboards, meaning a flexible layer with large surface measure. The sound insulation can be improved, for example, by • a reduction of the surface connecting points of the individual layers (paying attention to statically required spacing); • use of flexible bearing profiles such as spring rails, metal stand flexible shells; • use of heavy flexible panelling such as plasterboards; • use of soft insulating material in hollow spaces; • increasing the shell spacing. Figure 1 – The ceiling test bench in the sound testing lab and arrangement of the measuring instruments
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