Using barrier-adjacent measurements and predictions to determine effects of small gaps in highway noise wall

Noise walls are installed along highways to reduce highway traffic noise in adjacent communities. Based on installation or aging effects, some noise walls contain small gaps between panels. Applying traditional barrier insertion loss measurements comparing sections with and without gaps may not be possible due to site conditions. For this study, barrier-adjacent sound levels were collected at gap locations and comparable reference (non-gap) locations to determine the gap effect immediately behind the barrier. Two methods are then applied to determine how these gap effects translate to nearby communities. Both broadband and spectral sound levels are analyzed to determine that the effects of a small gap (up to 0.5 inches in height and 10 inches in length) can be up to 2 dB near the barrier but diminish rapidly with distance.