Noise barrier

[1] In the late 1960s, analytic acoustical technology emerged to mathematically evaluate the efficacy of a noise barrier design adjacent to a specific roadway.

By the 1990s, noise barriers that included use of transparent materials were being designed in Denmark and other western European countries.

Possibly the earliest published work that scientifically designed a specific noise barrier was the study for the Foothill Expressway in Los Altos, California.

By the late 1970s, more than a dozen research groups in the U.S. were applying similar computer modeling technology and addressing at least 200 different locations for noise barriers each year.

The acoustical science of noise barrier design is based upon treating an airway or railway as a line source.

Several different materials may be used for sound barriers, including masonry, earthwork (such as earth berm), steel, concrete, wood, plastics, insulating wool, or composites.

Within 15–50 m from the roadside, air pollution concentration levels at the lee side of the noise barriers may be reduced by up to 50% compared to open road values.

The deceleration and the deflection of the initial flow by the noise barrier force the plume to disperse horizontally.