Acoustic traffic control
Introduction
A noise barrier is an exterior structure designed to reduce noise pollution. It is commonly called sonic wall or sound barrier. These devices are effective methods of road noise mitigation, and mitigation of railroad and industrial noise sources (there would be others such as cessation of activity or the use of source controls). In the case of surface transportation noise, very little can be done to reduce the intensity of the noise source (this could be by increasing the percentage of hybrid vehicles and electric vehicles, a strategy that works only at low to moderate traffic flow speeds). (started after noise regulations") in the early 1970s.
History
Noise barriers have been built intuitively, but not frequently, in the US since the mid-century, when vehicular traffic worsened. In the late 1960s the science and technology of acoustics emerged from mathematical evaluations of testing the effectiveness of a noise barrier design for the adjacency of a specific road.
The best thing about those early computer models was considering the effects of road geometry, topography, vehicle volumes and their speeds, traction mix, road surface type, and micrometeorology. Several groups of researchers within the US developed variations on the modeling techniques: Caltrans in Sacramento, California; the ESL group inc.) in Palo Alto, California; Bolt, Beranek and Newman group[1] in Cambridge, Massachusetts and a research team from the University of Florida. Possibly the first published work on scientifically designed noise barriers was the study for the Foothill Expressway in Los Altos, California").[2].
Numerous case studies in the US appeared in dozens on different existing and planned highways. Many of those studies were commissioned by the State Highway Department and conducted by one of the four groups of researchers mentioned above.
In the late 1970s, about a dozen research groups in the US applying similar computer modeling technologies made at least 200 different locations in one year of noise barriers. As of 2006, this technology is considered a standard in highway noise pollution assessment, but, remarkably, the nature and safety of the computer model used is closely identical to the original 1970 versions of the technology.