Environmental noise also known as noise pollution is defined as any unwanted sound waves generated by the vibration of an external object that penetrates the ear canal. Environmental noise is ubiquitous in modern life across the globe. While low-level environmental noise is virtually harmless, noises above a decibel level of 60 can cause psychological, emotional, and even physical damage. Noise pollution can ultimately lead to hearing loss, sleep disorders, and heart disease. There have even been scientifically proven observations that show a direct link between noise pollution and heart health. In fact, a modest decrease in noise pollution can have a measurable positive effect on our overall heart health. Modern society has been aware of these facts and began studying the adverse impact of environmental noise on humans dating back to the 1960s. Initial sound barriers were created to solve the problem of the ever-increasing noise resulting from the American car boom.
Materials used to create sound barriers
The engineering of sound barriers varies and is dependent upon the sound source that ultimately generates the sound waves that are causing or has the potential to become noise pollution. Sound waves move through space in what is described as a line source. A line source defines or describes how sound waves emit from their source. In general, sound barriers are designed to block the forward movement of the natural waves from its source to our ear canals. Traditionally sound barrier materials have been composed of materials such as stonework, concrete, plastic, steel, and wood to name a few. However, the properties of the various materials used to construct the sound barrier naturally play a considerable role in the effectiveness of the barrier itself.
Types of common sound barriers
Sound barriers can generally be categorized into two categories or types, reflective and absorbent. Reflective sound barriers do just that; they reflect or diffract the sound waves back into the environment they are designed to protect. Literally, .01% of the sound is actually eliminated, leaving the other 99.9% to be reflected back into the atmosphere. Concert sound barrier walls reflect sound waves. Reflecting sound waves does not remove or reduce the noise but dissipates the sound throughout the environment, which is not ideal. Sound absorbing materials such as acoustic cotton, specially engineered foam, particular types of wood, quiet boards, and acoustic fiberglass are much more effective in the elimination of noise pollution.
Engineering of sound barriers
The construction of sound barriers depends heavily on the types of sounds they are being constructed to block or quiet. When engineers are designing sound barriers, there are many factors to consider, but the most crucial variable is the materials to be used in the construction of the barrier. Concrete sound barrier walls are both expensive to contract and not very effective at what they are designed to do. Concrete is a very heavy material, to begin with, so the transporting of concrete barriers increases the overhead costs. Consequently, the use of concrete sound barrier walls is not cost effective.
Why sound absorbing materials are better than sound reflecting materials
Using materials that naturally absorb sounds are not only more effective in the ability to lessen noise pollution, but they are generally cheaper and much easier to transport due to their lightweight. Sound absorbing materials effectively absorb the sound waves that travel toward them which negates the sound wave energy. The energy that is absorbed is converted into heat while the rest is moved through the materials lessening the decibel levels.