Optimisation of railway noise barrier design using finite element and boundary element modelling methods

The prediction of environmental noise barrier insertion loss (IL) is commonly undertaken from widely available empirical methods derived from measurements and geometrical acoustic approximations. The accuracy of these methods is limited when analysing non-standard design parameters, such as geometry; characteristics and location of sound absorbing materials; or diffraction effects close to the barrier. This article presents a new methodology to optimise the design of a railway noise barrier using a simplified numerical method. The numerical method is based on a two-dimensional hybrid finite element and boundary element analysis. The numerical method has been calibrated and tested against measurements of high speed trains. The model assumes an infinitely long train with pre-defined sound sources (e.g. rolling source, body aerodynamic, etc.). The numerical model quantifies the effect of various parameters upon the barrier IL including material properties; area and location of sound absorbing materials; diffraction over the barrier top; and analysis of energy build-up between train and barrier. These parameters are not easily quantifiable using standard methods and hence the innovation aspect of the methodology. The outcome of this study can be used to optimise and improve confidence in the detailed design of complex noise barriers.