| Although its presence lingered unaddressed for many | | | | noise emission standards for major sources of noise in |
| years, environmental noise is now recognized as a | | | | the environment, including transportation equipment and |
| significant health issue. Environmental or ambient noise | | | | facilities, construction equipment, and electrical |
| is unwanted or harmful outdoor sound created by | | | | machinery; and to recommend regulations for |
| human activities, including noise emitted by means of | | | | controlling aircraft noise and sonic booms. Also in the |
| transport - road traffic, rail traffic, air traffic - and from | | | | 1970s, the Occupational Safety and Health |
| sites of industrial activity. From delivery trucks to air | | | | Administration began to try to reduce workplace noise. |
| conditioners, we are constantly bombarded by sounds | | | | And over the past 30 years, the general public has |
| that go unnoticed for the most part. However, | | | | become increasingly aware of the hazards of |
| out-of-earshot should not mean out-of-mind. It is | | | | environmental noise, and its ability to combat it on an |
| precisely these innocuous environmental noises that | | | | individual and collective level.One of the most effective |
| should be sounding an alarm.Those involved with the | | | | environmental noise abatement technologies to be |
| more obvious noise sources such as airports, shooting | | | | developed is the noise barrier wall, or sound wall. |
| sports, manufacturing or even musical concerts have | | | | Sound walls are classified as reflective or absorptive. |
| long known the detrimental effect of extreme noise | | | | Hard surfaces such as masonry or concrete are |
| levels on long-term hearing. Only recently, however, | | | | considered to be reflective. This means most of the |
| has environmental noise been thoroughly researched | | | | noise is reflected back towards the noise source and |
| for its affect on our mental and physical health - and | | | | beyond. A barrier wall such as the Sound Fighter(R) |
| the findings may surprise you. But to gain a better | | | | LSE 2000 with a porous surface material and |
| understanding, one needs a basic education on what, | | | | sound-dampening content material is said to be |
| exactly, noise is.Noise intensity is measured in decibel | | | | absorptive. This means little or no noise is reflected |
| units. The decibel scale is logarithmic; each 10-decibel | | | | back towards the source or elsewhere.Sound walls |
| increase represents a tenfold increase in noise | | | | are performance rated in two categories: Sound |
| intensity. Human perception of loudness also conforms | | | | Transmission Class (STC) and Noise Reduction |
| to a logarithmic scale; a 10-decibel increase is | | | | Coefficient (NRC). The STC determines the amount of |
| perceived as roughly a doubling of loudness. Thus, 30 | | | | noise energy transmitted through the wall material. The |
| decibels is 10 times more intense than 20 decibels and | | | | NRC determines the amount of energy absorbed by |
| sounds twice as loud; 40 decibels is 100 times more | | | | the wall material and the amount of energy reflected |
| intense than 20 and sounds 4 times as loud; 80 | | | | back towards the source.Walls having STC ratings of |
| decibels is 1 million times more intense than 20 and | | | | 30 or more means that less than 0.1 percent of the |
| sounds 64 times as loud. Distance diminishes the | | | | noise energy is transmitted through the barrier material. |
| effective decibel level reaching the ear. Thus, | | | | Many State Department of Transportation |
| moderate auto traffic at a distance of 100 ft (30 m) | | | | specifications require minimum STC ratings of 24.NRC |
| rates about 50 decibels. To a driver with a car window | | | | measures the amount of sound energy absorbed and |
| open or a pedestrian on the sidewalk, the same traffic | | | | measures the amount of sound energy reflected back |
| rates about 70 decibels; that is, it sounds 4 times | | | | towards the source. NRC ratings will range between 0 |
| louder. At a distance of 2,000 ft (600 m), the noise of | | | | (100% reflective) to 1 (100% absorptive). A wall with an |
| a jet takeoff reaches about 110 decibels-approximately | | | | NRC rating of .85 means the wall absorbs 85% of the |
| the same as an automobile horn only 3 ft (1 m) away. | | | | noise and reflects 15% of the noise back towards the |
| ¹Subjected to 45 decibels of noise, the average | | | | source. NRC ratings equal to or greater than .85 are |
| person cannot sleep. At 120 decibels the ear registers | | | | considered to be good sound absorbers and are often |
| pain, but hearing damage begins at a much lower level, | | | | used as the minimum requirement when considering |
| about 85 decibels. The duration of the exposure is also | | | | absorptive walls.A good sound wall is a |
| important. There is evidence that among young | | | | sound-absorbing wall with a STC rating of 30 or more |
| Americans hearing sensitivity is decreasing year by | | | | and a minimum NRC rating of .8.Is a sound wall the |
| year because of exposure to noise, including | | | | best mitigation option for every application? Certainly |
| excessively amplified music. Apart from hearing loss, | | | | not. There are effective mitigation tools for any |
| such noise can cause lack of sleep, irritability, heartburn, | | | | situation - from earplugs to ceiling tiles. But for many |
| indigestion, ulcers, high blood pressure, and possibly | | | | outdoor applications such as traffic, manufacturing, |
| heart disease. One burst of noise, as from a passing | | | | compressor and commercial retail noise, nothing |
| truck, is known to alter endocrine, neurological, and | | | | outperforms a well-engineered and efficient absorptive |
| cardiovascular functions in many individuals; prolonged | | | | sound wall.* * *¹ Infoplease, Copyright © |
| or frequent exposure to such noise tends to make the | | | | 2000-2006 Pearson Education, publishing as |
| physiological disturbances chronic. In addition, | | | | Infoplease.² H.I.N.S., IncMurray Stacy is Vice |
| noise-induced stress creates severe tension in daily | | | | President of Sound Fighter Systems, LLC, which has |
| living and contributes to mental illness.¹Does this | | | | been researching, designing and manufacturing highly |
| mean we are doomed to a noise-filled life of stress? | | | | efficient absorptive noise barrier walls since 1973, |
| Fortunately, no. Noise is now recognized as a | | | | making it the oldest established manufacturer of such |
| controllable problem that can be minimized via varied | | | | products in America. Sound Fighter walls have been |
| abatement technologies. In the United States the Noise | | | | produced for unique noise mitigation applications around |
| Control Act of 1972 empowered the Environmental | | | | the world, and several of the company's walls are in |
| Protection Agency to determine the limits of noise | | | | their 30th year of effective service. |
| required to protect public health and welfare; to set | | | | |