Effect of Wind and Temperature on Traffic Noise Levels With and Without a Noise Barrier

Noise studies conducted under the requirements of Title 23, Part 772 of the Code of Federal Regulations, “Procedures for Abatement of Highway Traffic Noise”, do not account for meteorological conditions. However, it is widely accepted that at distances of 300 feet (ft) (98.4 meters [m]) and further from the roadway, atmospheric effects have an influence on measured sound levels. This paper describes the influence of meteorological conditions on receptors located both adjacent to and at distances exceeding 300 feet (98.4 m) from the highway through the results of measurements for two noise studies located in California and Arizona. Of the two described studies, both have sites that are relatively at-grade with respect to the adjacent highway, but one site is located behind a sound wall. Based on preliminary comparison between the two cases, air temperature effects appear to be primarily dependent on distance from the roadway and may or may not be affected by the placement of a barrier. Wind effects on traffic noise levels show possible dependence on the presence of a barrier.