| Popis: |
This paper compares the performance of a restricted number of barrier shapes and types under controlled experimental conditions and describes theoretical models. In particular, the attenuation of absorbent barriers on ground, of finite length barriers on the ground, of parallel noise barriers, of earth berms, as well as the effects of atmospheric conditions on barrier performance outdoors are briefly reviewed. An absorbent barrier is obtained when a thin barrier is covered with absorbent material, on the source or receiver side, or both. The attenuation provided by a partial barrier is complicated by additional ray paths. Parallel barriers can degrade the performance of the single barrier; however, absorbent material can be used to recover the loss in performance. Earth berms covered with grass are particularly effective barriers at higher frequencies, however, atmospheric turbulence places a limit on the amount of attenuation achieved outdoors. At longer distances, barrier performance is degraded during ... |
