Do Sound Barriers Work?
Low frequency sound bends around obstacles and through openings. Each meter of height on a sound barrier will reduce noise by one decibel. But sound barriers are expensive, costing between $1 million and $1.5 million per mile. Single barriers reflect sound and can make a noise problem worse in front of a barrier, says Luc Mongeau, Professor of Mechanical Engineering at Purdue University. But absorptive barriers, used on both sides of the road, will substantially reduce sound. It is preferable to treat the source of the noise (tire noise) rather than to treat the path of the noise, says Mongeau, who specializes in acoustics and noise control. Quiet Pavement Design Single-layer porous asphalt has been implemented in the Netherlands, France and Germany. The single-layer porous asphalt consists of a 30 to 40 mm thick gap-graded mix with 20 to 30 percent air voids. It provides a 3 to 5 dBA noise reduction. This type mix costs about 10 to 25 percent more than conventional dense-graded asphal
