Effect of large bus body reflection on sound barrier efficiency for road traffic noise control: a simulation study

Assessment of road traffic noise (RTN) generally approximates vehicles as point sources, including in the setting of roadside sound barriers (SBs). However, when a large passenger bus passes on a road section with an SB, strong reflected sound waves emerge between the bus body and the SB, reducing the effectiveness of the SB. In this study CadnaA software was used for simulating the sound field distribution formed by such reflections. Because a large bus cannot be approximated as a point source, multi-point noise measurement results of the near-field position of the body of a moving bus were adopted for simulating the actual three-dimensional bus by distributing small-area sources approximately at the near-field different positions near the bus body surface. For a bus moving on a road past an SB, noise distributions were simulated for three scenarios: 1) without an SB, 2) with a smooth reflection-type SB, and 3) with an absorption-type SB. This study presents important insights for establishing RTN SBs.