Changes in Sound Due to Noise Barrier Reflections

As part of a national study on noise barrier reflections, data were collected at multiple sites across the U.S. to characterize the effect of barrier reflected noise for both reflective and absorptive noise barrier walls. It was determined that overall traffic noise levels increase slightly near the road and up to a few decibels at greater distances, due to installation of a barrier on the opposite side of the road. In many cases, residents have found reflected noise to be objectionable, even with small increases in overall sound level. This paper exposes features in the spectral content of received sound with a barrier present that may help to explain adverse effects. The analysis includes use of spectrograms and identification of comb filtering.