Numerical simulation of the sound reflection effects of noise barriers in near and far field

This paper deals with the first stages of the development of a new test method for evaluating the reflectivity performance of noise barriers. The reflectivity performance describes the increase in sound level at a receiver due to the presence of the noise barrier. First the current test method for sound reflectivity is simulated with three different numerical simulation models (time and frequency domain). It is shown that a good insight can be obtained in the reflection patterns and the measurement process. The Reflection Index (RI, omparable to the reflection coefficient) in the near-field is dependent on geometry and level of absorption of the material on the barrier. Preliminary results are presented for Reflection Indices in the far field for several types of barrier. From these results the effect of the shape of the barrier can be distinguished. Further research will involve the matching of simulated RIs with measured RIs and the extrapolation from RIs in the near field to RIs in the far field.