Augmenting Road Noise Engineering Methods using the Boundary Element Method

Exposure to excessive noise is correlated with higher rates of annoyance, sleep disturbance, and other negative health outcomes. Accurately calculating road noise in a complex urban environment is fundamental to assessing potential noise mitigation devices and reducing overall noise exposure. However, computing sound propagation in this setting is difficult because cities have complicated geometries and large domains. For example, engineering methods such as ISO-9613-2 or NMPB-Routes-2008 efficiently estimate sound levels but cannot model complex geometries like a T-shaped barrier. In addition, detailed approaches such as the boundary element or the finite-difference time-domain methods produce precise results for any geometry but rapidly become too expensive as the frequency and domain size increase. Using a hybrid formulation can alleviate these problems. Specifically, the boundary element method yields a table of the impacts of the domain's involved structures for a range of source and receiver positions and frequencies. Interpolating this table, the engineering method adjusts the predicted sound level for each path. This paper discusses and evaluates the main approximations of this technique.