Three-dimensional analysis of a noise barrier using a quasi-periodic boundary element method.

Two-dimensional (2D) numerical models are often used to estimate the environmental noise attenuation of a roadside barrier. The prediction of noise barrier attenuation using a 2D boundary element model assumes an infinitely long barrier with constant cross section. However, for barrier geometries that do not have constant cross section in the third dimension, three-dimensional (3D) models should be used for greater accuracy of noise reduction due to the barrier. The size of a numerical model and hence its computational cost can be significantly reduced using a 3D quasi-periodic structure, whereby the structure is truncated using a finite number of periodic sections. In this study, a quasi-periodic model developed using the boundary element method is used to predict the acoustic performance of 3D noise barriers. The convergence behavior of the quasi-periodic model is discussed. Results from the quasi-periodic model are compared with results from both a 3D analytical model and a 2D finite element model, showing good agreement. Quasi-periodic models of different noise barrier designs are developed and their acoustic performances in terms of frequency and receiver positions are discussed. The quasi-periodic boundary element method provides a computationally efficient tool to examine the acoustic performance of 3D noise barrier designs.