FEM modelling of sound reduction index in partition CLT wall

Abstract: Constructing buildings with wood brings many advantages, especially regarding environmental aspects, which has brought an up-rise in these types of structures. However, one of the main issues regarding wooden structures is its tendency to perform poorly acoustically in lower frequencies compared to heavier structures. This often leads to unwanted noise levels which could be avoided in earlier design stages with tools that predicts the vibroacoustic response. Predicting the vibroacoustic response of buildings constructed with wood is challenging much due to its irregular material parameters. Wood is an orthotropic material meaning it has varying stiffness and strength in different directions. It is also an organic material which brings a variation in stiffness and strength not only between different species of trees, but also within the same species. In order to have building elements with less variation regarding these parameters, different engineered wood products (EWPs) has emerged on the market during the last decades. Cross-laminated timber (CLT) is an increasingly popular product in the wooden building industry which demands for more research of its vibroacoustic performance. In this thesis a finite element model was created to predict the airborne sound insulation of a five-layer CLT slab in the low-frequency range of 1-200 Hz. Different measurements, such as experimental modal analysis and sound pressure level measurements, were performed to calibrate the model as well as validate the results obtained from it. The thesis shows that the airborne sound insulation can be predicted with a finite element model, but only together with measurements determining the material parameters and damping of the CLT under evaluation. The damping was shown to have a crucial impact on the results. The airborne sound insulation is determined in the model at the excited resonance frequencies of a plate due to a pressure load resembling airborne sound.