Highway sound barriers are often not a high priority in the everyday lives of the average citizen, but they have the ability to be able to reduce noise pollution effectively enough to allow a comfortable noise level to be achieved.
What is a highway sound barrier?
A highway sound barrier is a solid obstruction which is built between the highway and a sound sensitive area to protect the inhabitants from noise pollution. Although they do not block all noise from the highway, they are the most effective method of reducing overall noise levels. Effective noise barriers are said to reduce levels by around 5 to 10 decibels. This means that the average road noise could be reduced from 60db to 50db, which is about the same as a dishwasher! A sound barrier can be made from earth berms, which are mounds of mud, stone and vegetation that have been built up on the roadside. This kind of barrier makes it difficult for the sound waves to enter into the protected area, as they are built high enough that the noise has to force its way over; a behaviour that is not common in the science of sound waves. The earth berm can be reinforced with concrete panelling to create a more structured sound barrier.
Another type of sound barrier is a tall panelled wall that surrounds the gap between the roadside and the protected area. It can be made using a metal structure filled with concrete, or with a fibreglass composite panelling, filled with noise absorptive acoustic shells. The typical earth berm is actually more effective at reducing sound, with a 3 decibel difference from that of the vertical concrete walls. Depending on the amount of space, earth berms are often the best choice when it comes to sound barriers as they look more natural and are more effective at reducing noise pollution.
How do they work?
A highway sound barrier can reduce noise pollution which enters into a residential area by absorbing the sound, transmitting it, reflecting it back across the highway or forcing it to take a longer path over the earth berm or wall. In order for the sound barrier to work effectively, it needs to be tall enough and long enough to block the view of the highway from the area that needs to be protected. The ends of the sound barriers are good spots for sound to creep its way past. To prevent this from happening, the barrier should be at least eight times as long as the distance from the protected area to the barrier. In some instances, openings are built in the sound barriers for driveway connections or intersecting streets. However, this destroys their effectiveness as it stops the sound from being able to travel down the length of the barrier, and allows it to enter into the protected area. If a sound sensitive piece of land is on a hillside and is above the top level of the barrier, it will not be effective at reducing sound. For this reason, it is often not possible to reduce the noise pollution to a low enough degree to warrant the building of a new highway sound barrier.
Sound barriers are an effective way of enabling a quieter life for residents that live close to a highway and remain to be one of the best ways of reducing overall noise pollution.
By g_sakketos from Pixabay