The completion of the largest Ohio Department of Transportation traffic noise abatement project in 1995 was met with public controversy over the effectiveness of the noise barriers. A public opinion survey was designed to obtain the perceptions of the residents in the project area. In a departure from most surveys of traffic noise barrier effectiveness, the coverage was not limited to the first or second row of houses, but was extended to 800 m on each side of the roadway. It was found that the larger survey area was needed to avoid misleading conclusions. Overall perceptions of noise barrier effectiveness were found to vary with distance from the roadway and with noise barrier configuration.
Sound propagation through the gap produced by two parallel vertical barriers with overlapped ends is formulated for traffic noise sources. The analysis identifies both source and receiver regions according to the mechanisms that influence noise propagation in the vicinity of an overlap gap. A method to account for the contributions from the various source regions for a given receiver location is described. The derived method can be implemented using various equations for sound propagation. The results of using equations approved by the United States Federal Highway Administration for traffic noise propagation are given. Uncalibrated predictions are compared with field measurements for up to 30 receiver positions from each of four overlap gaps. The relative importance of contributions from reflected rays to the noise levels at receiver positions is given. The analysis confirms the initial hypothesis that a commonly used strategy of overlapping barriers by an amount equal to two or three times the overlap width is useful for controlling line-of-sight propagation but ignores the substantial effect of reflections.
Sound propagation through the gap produced by two parallel vertical barriers with overlapped ends was formulated for traffic noise sources. The method accounts for sound propagated from vehicle source positions for a maximum of ten roadway lanes. Six receiver regions were considered based on potential receiver locations with respect to a gap. The analysis identified both source and receiver regions according to the mechanisms that influence noise propagation in the vicinity of an overlap gap, which can result in: direct rays, diffracted rays from the top edge of one barrier, diffracted rays from the top edge of both barriers, rays reflected between the barriers, and rays that are both reflected and diffracted. The derived method could be implemented using various equations for sound propagation. The results of using equations approved by the United States Federal Highway Administration (FHWA) for traffic noise propagation are given. Field measurements for up to 30 receiver positions from four overlap gaps were compared with uncalibrated predictions. The equivalent continuous levels, A weighted, were overpredicted by 2–3 dB. When the analysis was based on an octave band characterization of the source, the mean overprediction was reduced to less than 1 dB.
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