Research on the well at the top edge of noise barrier

Wells mounted on the top edge of barrier could improve the noise reduction effect of the barrier. In order to research the characteristics of the well, the 2D boundary element method (BEM) was adopted, the insertion loss (IL) of different type of barriers were calculated, the effect of well was analysed. Results showed that, almost 1.5 dBA of the IL is aroused by the reflect sound of the well. So, it is important to improve the sound field inside the well to improve the noise reduction effect of the barrier. The sound field inside the well depends on the sound diffraction effect, therefore, the characteristics of sound field diffracted by a single edge was analysed by the geometrical theory of diffraction (GTD) method. Then the effect of well width on the noise reduction effect was discussed according to the sound diffraction loss. To verify the discussion conclusions, the noise reduction effect of barrier with different width of well was simulated and compared. In addition, experiments were also carried out in a semi-anechoic chamber using full-scale models. Both the experimental and simulation results show that, to play a better role of the well, the well width should be greater than 1/3 of the well depth.