In the world today, noise has become one of the most pervasive forms of environmental pollution. Noise is everywhere. It affects our lives at home, at work and at play. Wherever people live there is noise. Noise, by definition, is any unwanted or excessive sound. It can be a nuisance, interfering with sleep, work or recreation, and in extreme situations, it can lead to anxiety, stress and other health problems.
The dB(A) scale begins at zero, which represents the faintest sound that can be heard by humans with very good hearing. Conversations take place in the 50 dB(A) range and a chainsaw whines at about 100 dB(A). Normal highway traffic sounds rank about 75 dB(A) and jet airliners around 90 dB(A). For most people, discomfort starts in the 70 to 80 dB(A) range, with the threshold of pain around 140 dB(A). The Federal Highway Administration (FHWA) has chosen 67 decibels as the point where state and federal agencies must consider reducing the noise level.
Road Noise Abatement Options
When a noise barrier wall is constructed, there is a significant noise drop immediately behind the wall. The problem is that those buildings that are on hillsides, at intersections or driveways or anywhere there is an opening in the wall, will not benefit from noise reduction. In some cases where noise walls are built parallel to one another, noise reflections or echoes of the sound waves off the opposite wall can actually increase noise levels at a location near the highway.
Studies show that when all these inefficiencies are considered, the average noise reduction from noise barriers is approximately 7 dB(A). Other noise abatement options such as vegetation or green walls have the same limitations.
Research in the U.S. and Europe shows that a Stone Matrix Asphalt (SMA) or Open-Graded FrictionCourse (OGFC) mix will reduce highway noise by 3 to 5 dB(A). To the average person, this reduction is the same as doubling the distance between the source of the noise and their location.
When comparing the noise reduction that is possible by choosing asphalt pavement-up to 7 dB(A) -we see how much more practical pavement surface selection is than construction of noise barrier walls.
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Asphalt is one of the indispensable materials of life in America. Want proof? Think about the fact that 94 percent of the paved roads in America are surfaced with asphalt.