Ljudisolering i dubbelväggskontruktioner av KL-trä : Uppskatta reduktionstal med analytisk modellering

Sammanfattning: Rapidly growing cities require that new residential buildings be created at a matching pace. Moreover, ambitious environmental goals not only call for these buildings to be constructed swiftly, but also in a sustainable manner. Cross-laminated wood, abbreviated CLT, may partly offer a solution to these challenges. During a period when wood was prohibited to serve as a framework material in buildings higher than two stories, the research examining wood as a building material suffered a setback. While the interest in wooden buildings has increased in recent years, there are still uncertainties regarding several of the material’s properties, such as its acoustics. Being able to predict whether a structure will meet the desired acoustic requirements, is vital to contractors and clients in the building industry, as later reconstructions often result in considerable added costs and delays. Thus, tools that help predict acoustic properties are in high demand and may help wood become a more attractive choice of building material. Aiming at decreasing the total thickness of a double-wall without compromising its sound insulation ability, an experiment examining the effects of perforation of a CLT panel and its impact on the sound reduction index (SRI), was conducted. Results indicated that it may be possible to decrease the total thickness of a double wall by perforating the panel, while maintaining and in some cases, increasing the SRI. This study is based on an analytical calculation model which predicts the sound insulation properties of single- and double walls, measured in SRI [dB]. The original model was produced by Sharp and later modified by Ljunggren to obtain a better match for CLT panels. The sample data, provided by the company Martinsons AB, consisted of 32 unique double-wall configurations of which the SRI was modelled. As the original model only applied to configurations assuming total insulation of the cavity, an extension was calculated to apply to configurations comprising no or partial insulation. To validate the model, results were then compared to available data from onsite measurements provided by Tyréns, as well as calculations by Ljunggren. As comparable data is limited and most modelled configurations had no corresponding onsite measured SRI, the results of this study may serve as an indication of what sound insulation quality to expect for those configurations. The predicted SRI for which a corresponding measured SRI did exist, showed good agreement, with deviations of 1-2 dB. Compared to measurements conducted by Tyréns, the modelled SRI were approximately 3-6 dB higher. Measured SRI are under the influence of flanking transmission which often results in it being the lower value, when compared to modelled SRI. However, the relative difference between the two values can still serve as a useful tool. To strengthen these findings and confirm the validity of the model, further research examining a wider range of measurements and comparisons with modelled results should be conducted.