Analysis of the vibroacoustic characteristics of cross laminated timber panels using a wave and finite element method

This paper presents an analysis of the vibroacoustic characteristics of Cross-Laminated Timber (CLT) panels using a Wave and Finite Element (WFE) method. Two WFE modelling approaches are investigated: the first models each layer of the panel as a homogeneous orthotropic material, whereas the second approximates the entire panel as a single equivalent homogeneous orthotropic material. Results are also compared to those of a thin, orthotropic plate model which is a model commonly used in the literature. The three methods are used to calculate the plane-wave and diffuse-field sound transmission loss of a CLT panel. It is seen that all models are in reasonable agreement at low frequencies, but that the models predict different sound transmission loss at higher frequencies. The dispersion curves and mode shapes of the free waves propagating within the in-vacuo panel are predicted for both WFE models. These results are used to interpret the vibroacoustic behaviour of the panel. It is observed that, at high frequencies, the vibroacoustic behaviour of the panel is complicated, with many wave modes cutting on. This behaviour is not modelled by the equivalent orthotropic plate model, which is incapable of capturing those higher-order waves. The contributions to the sound transmitted by the various wave modes are estimated and the most significant modes identified. Finally, predictions of the sound transmission loss of a number of CLT panels are calculated using the layer-wise WFE modelling approach. These predictions are compared with experimental measurements, showing reasonable agreement. The predictions clearly capture the important coincidence dips present in the measured spectra, although there are some minor discrepancies between the measured and predicted levels and coincidence frequencies. These discrepancies may be partially due to the uncertainty and variability of the material properties of wood. A series of simulations are performed to investigate the effect of the uncertainty of different structural material properties on the sound transmission loss. (C) 2020 Elsevier Ltd. All rights reserved.