Optimization of Noise Barrier Reflection Properties

Noise barriers are a common tool to mitigate roadway and railway noise.They are characterized by extrinsic parameters, e.g., the insertion loss, and by intrinsic parameters, i.e., the sound insulation index as defined in the standard EN 1793-6 and the sound reflection index as defined in thestandard EN 1793-5.The reflection index mainly depends on the surface structure of a noisebarrier's front side and on the acoustic absorption properties of the materials in use.In this study, a noise barrier was optimized to achieve a maximal DLRI, which is the attenuation of the reflected sound in dB, weighted with the road traffic noise spectrum (EN 1793-3).For the optimization, an analytical model similar to the transfer matrix method was used.Its low computational effort allowed to test many different geometries and absorber parameters.The best performing setup was verified with the finite element method (FEM)which was implemented in the open source software FEniCS.Finally, a prototype of the optimized noise barrier was built and measured according to the main principles of the standard EN 1793-5. Results ofthe analytical calculation, the FEM simulation, and the measurement werecompared.