Numerical Analysis of the Efficiency of Different Median Barrier Models in the Presence of a Plain Roadside Noise Barrier

Roadside noise barrier as the noise control solution is extensively applied to reduce noise pollution. Median barrier like roadside barriers can make insertion loss at the receiver's area making a shadow zone behind the screen. However, the performance of roadside barrier can be affected by erecting a median barrier. Mainly a median barrier is considered as an extra structure to decrease the cross median crashes at highways. The aim of this study was to investigate the effectiveness of some treatments such as absorbent material and diffusers on various median barriers shapes. A 2D boundary element method was used to analyze the designed median barrier effects. Application of grass on the top surface of median barriers with even cap was more effective than those median barriers that had uneven cap. Utilizing Primitive Root Diffuser (PRD) and Quadratic Residue Diffuser (QRD) on the stem surface of median barrier has high efficiency due to cancel outing multiple reflection effects between roadside barrier and median barrier by 2.2 to 2.7 dB (A), while no improvement could be seen at median barriers with QRD and PRD tops. Finally, it can be stated that the performance of most median barriers were increased using the reactive surfaces on the stem sides of the barrier, while the top surface treatment was not very effective in this kind of screens.