Stopping SOUND The advantages of highway precast wall barriers by Tom Kuckhahn, PE Photo courtesy Fabcon FEDERAL, STATE, AND LOCAL SPECIFIERS CONTINUALLY SEEK AFFORDABLE, DURABLE, AND AESTHETICALLY PLEASING WALL SOLUTIONS TO BORDER BUSTLING HIGHWAYS AND ADJACENT NEIGHBORHOODS. THE PRINCIPAL PURPOSE OF THESE IS TYPICALLY TO PROVIDE CITIZENS WITH A VISUAL BARRIER TO THE HIGHWAY AND SOMETIMES TO MITIGATE TRAFFIC NOISE. Today, highway barriers cover thousands of miles of federal roadways. When the walls first began to appear in the 1960s, they were modeled after wooden fences. Now, things have changed––according to the Federal Highway Administration (FHWA), almost half of the highway walls constructed in North America to date are made of concrete. 1 While wood, metal, brick, and masonry block also comprise some of the roadway walls sprawling the country, concrete panels have emerged as a preferred solution that meets many affordability, durability, and aesthetic specifications and preferences. Limiting the noise In addition to functioning as a visual shield, highway walls serve as barriers to help break the path of sound traveling from freeways to neighboring homes and buildings. Most highway noise barriers force sound to travel a longer path over and around the barrier. Effective highway walls typically reduce sound levels by five to 10 dB. Since sound levels are measured using a logarithmic scale, a reduction of nine decibels 32 the construction specifier | january 2013 CS_Jan2013.indd 32 12/12/12 9:33:48 AM