EFFECTIVENESS OF NOISE BARRIERS

摘要

Transportation activities are one of the most commonly occurring sources of noise outdoors. Noise levels from these transportation sources are not usually sufficiently high to cause permanent hearing loss in communities affected, but they may cause considerable annoyance and activity interference. For example, a large number of persons worldwide are exposed to outdoor time-average A-weighted sound levels greater than 65 dB. The use of barriers has proven an effective method of abating transportation noise. A recent Ⅰ-INCE Working Party concluded that the most common values for insertion loss range between about 5 to 12 dB. Barrier height is of fundamental importance to the effectiveness of a barrier. Proximity of source/receiver relative to the barrier is also of fundamental importance to the insertion loss provided by a barrier. Sound-absorbing material may provide addition insertion loss. Parallel barriers can degrade the performance of the single barrier; however absorbent material can be used to recover some of the loss in performance. Finally, atmospheric effects can degrade the performance of a barrier and places an upper limit on the amount of insertion achieved outdoors. This lecture will review the various factors affecting the effectiveness of noise barrier.