Areawide dynamic traffic noise simulation in urban built-up area using beam tracing approach

Modeling areawide traffic noise in both space and time domain is a tedious work, especially in urban built-up area. A smart, accurate and rapid method was developed specifically for fixed grid sources and receivers(S-R), which consisted of the precomputed S-R attenuations in off-line, dynamic traffic noise simulation in real time and a database to connect two parts together. In off-line part, beam tracing approach was used to simulate sound propagation among buildings, taking multiple reflections and diffractions into consideration. Firstly, the spatial subdivision was used to subdivide 2D space into a series of order triangles, and then beam tracing algorithm recursively traced beams through these triangles, which was represented by beam tree data structure. In real-time part, the dynamic simulation of traffic provides time-variant input of traffic flow parameters to vehicle emission model, which was then assigned to the nearest source. After deducing S-R attenuations from database, dynamic immissions at grid receivers are obtained by summing up sources inside their circular viewport. Therefore, the outputs (Ln, Leq and LNP) were available to assess the noise pollution levels on a spatial and temporal scale. A part of Zhujiang New Town in Guangzhou was chosen as a validation area, measurement results were in general good agreement with simulations.