Influential Factors and Rules for Insertion Loss of High-Speed Railway Noise Barriers

Based on the boundary element method and the train noise sources identified by a beam-forming noise source system, a numerical prediction model was established to study the factors and rules relevant to the insertion loss of high-speed railway noise barriers. The effects of noise source locations, noise barrier heights, shapes, and absorbing boundary conditions were investigated. The improvement strategies based on the current structure of noise barriers were proposed. The numerical results show that the noise source height has a significant effect on the sound barrier performance. The sound barrier of 2.15 m height can only reduce noise coming from the lower part of the train. The insertion loss increases with the noise barrier height. When the height exceeds 6.15 m, the insertion loss reaches over 25 dB(A). The sound barriers with different cross sections are listed, according to their noise attenuation effect, i.e., Y-shaped barrier, tilted barrier, T-shaped barrier, inward folded barrier, vertical barrier and outward folded barrier. The Y-shaped barrier produces the highest performance with an increase of 0.7~1.5 dB(A) in insertion loss compared with the vertical barrier. Despite the shape of noise barriers, the absorbing boundary overall lead to more noise reduction than the smooth rigid boundary, but the noise reduction amount relates to the forms of sound barriers ranging from 0.3 to 6.4 dB(A).