Studies show that continued exposure to noise pollution can lead to adverse effects on human health. For instance, continuous exposure to noise levels above 85 dB can lead to hearing loss.
According to the Federal Highway Administration, freeways can generate sound levels between 70 to 85 dB, which remains a cause of concern for people who reside near the nation’s freeways.
To minimize noise and mitigate the effects of highway noise on those that live near freeways, the Department of Transportation set up highway sound barriers along America’s vast network of freeways.
But despite the crucial role they play, not many pay attention to sound walls unless something goes terribly wrong.
This article will discuss the history of these walls, along with the following:
What Are The Walls For?
Many wonder, what are noise barrier walls for? highway sound barrier walls are exterior structures that have been designed to reduce or eliminate noise in areas where noise pollution is substantial. They are made from sturdy materials such as fiberglass, brick, wood, metal, or concrete – the properties of which dictate the properties of the wall itself.
As the name suggests, the primary function is to create a barrier between noise coming from the freeway and inhabitants living on the other side of the wall. They are designed to provide protection against noise for those that populate areas near roadways, railways, or industrial complexes and mitigate the effects of noise without eliminating or stopping the operation of its source.
How Do They Work?
The concept behind sound barriers is relatively simple. Authorities set up a sturdy wall with a set thickness near the side of the road. As cars pass through, the sound waves they generate interact with the wall’s hard surface. The wall, in turn, will either reflect, absorb or allow the sound waves to pass through it, depending on its properties.
The extent of the interaction between the sound waves and the wall will also depend on the wall’s height. A taller wall provides a higher surface with which sound can interact. But since the wall’s height can never be infinite, a percentage of the sound waves are able to pass over the top and are scattered through a process called diffraction. These sound waves will become audible a considerable distance away from the wall.
The Birth of the American Freeway
The origins of these walls ties together with the development of the American Freeway. Although arguments can be made about the freeway’s true origin, experts believe that the first freeway that matches its definition was built in California.
The Arroyo Seco Highway opened in 1940 and was the longest roadway of its kind at the time. It ran between downtown Los Angeles and Pasadena and paved the way for forming early automobile culture in California. Today, this roadway is known as Interstate 110.
After the establishment of the Arroyo Seco Highway, similar roadways that connect to it were opened, increasing the volume of automobiles in the city while increasing access to nearby cities.
The Post World War II Era
During the early 1930s and 40s, automobile travel wasn’t so much about traveling fast from point A to point B. Instead, it was more about traveling at a leisurely pace, going on a scenic ride, and checking out the sights along the way. However, things soon changed after the end of the second world war.
Economic development after the end of WWII improved conditions inside the country dramatically. Infrastructure development kicked into full gear, which saw the nation’s freeway network increase exponentially.
Greater economic prospects further fueled technological innovations, especially in automobile manufacturing. From focusing on scenic rides, the people wanted to keep up with the rapid pace of growth, which meant having to travel at a more rapid pace. This resulted in a greater need for wider tires and lower cars as the need for speed required more traction on the roads.
Overall, greater accessibility to automobiles and the rapid expansion of freeways resulted in an exponential increase in the number of vehicles on the road constantly – all of which compounded to create more noise on the nation’s major road networks.
Creation of Highway Sound Walls
The greater number of vehicles traversing U.S. roadways became even more apparent in downtown Los Angeles. More automobiles on the road meant more noise, which would soon affect the entertainment industry.
The Cahuenga Boulevard Parkway opened in sections of the Arroyo Seco Highway in the mid-1940s and played a prominent role in setting up interventions for the noise around the city. This two-mile stretch of road traversed areas near the Hollywood Bowl. More cars going through the area resulted in an increase in loud, distracting noises that also affected performers and audience members, alike.
Dr. Vern O. Knudsen, a professor of acoustics at UCLA, worked with the California Department of Public Works to study the noise near the Hollywood Bowl and the impact it would have on day-to-day operations. The professor concluded the study by offering a recommendation that a wall or parapet needed to be set up to serve as a barrier against the noise. The walls, according to his recommendations, was to be placed along the southeast corner of the Bowl and needed to be at least 10-feet high to provide ample protection against the freeway noise.
As more stretches of freeway linked up via the Cahuenga Pass, the professor would write another paper 10 years after, reiterating the call for a barrier to protect against noises coming from the newly-established U.S. 101 Freeway.
The Noise Control Act of 1972
In 1972, legislation was passed that equipped the U.S. Environmental Protection Agency (EPA) with the authority to address sources of noise and issue noise emission regulations.
The Act remains in effect today, although it now lacks funding and notoriety. But during the time of its establishment, the Act altered the U.S. landscape considerably as it paved the way for the setting up of walls along freeways to address noise pollution in roadways across the country.
The Sound Fighter® Advantage
Traditional barriers along highways are made of reflective materials that allow sound ways to bounce off of them, creating even more noise on the road.
Sound Fighter® offers effective noise reduction and abatement solutions that absorb sound waves, eliminating them altogether. Learn more about how Sound Fighter®’s SonaGuard systems can reduce noise pollution along the country’s road and freeway network. Give us a call at 1-866-348-0833, or use this contact form to request a quote!