Evaluation Of Effects Of Noise Barrier Defects On Their Noise Reduction Efficiencies

In this study, in-situ performance of noise barrier on Taiwan national freeway was measured following procedures specified in ISO 10847. The measured in-situ performance was numerically evaluated by using the Traffic Noise Model (TNM) developed by Federal Highway Administration. By comparing measured data with numerical data, the adequacy of applying TNM to perform numerical evaluation on noise barriers was verified. It was found that TNM will overestimate roadside energy equivalent noise level (LAeq) measured in Taiwan. Yet, TNM can give satisfactory results in terms of the difference between beforeand after-installation comparisons. Numerical experiments were then executed to investigate effect of noise barrier defects on their noise reduction performance. Commonly observed noise barrier defects, viz. single panel missing and inadequate overlapping, were evaluated. It was observed from numerical simulation that these defects do have significant effects on noise barrier performance. Reduction on effective noise can be more than 3.5 dBA while width of broken barrier varied from 0 to 2 meters. On the other hand, inappropriate overlapping is observed to have about 3 dBA difference on effective noise reduction. It is inferred from current results that appropriate and swift remedy actions should definitely be done to reduce the impact of noise barrier defects onto adjacent residents.