Noise pollution is unwanted human-created sound that disrupts the environment. The dominant form of noise pollution is from transportation sources, principally motor vehicles, referred to as environmental noise. The word noise comes from the Latin word nausea meaning seasickness.

Sources of noise

Main articles: Roadway noise and Aircraft noise

The overarching cause of most noise worldwide is generated by transportation systems, principally motor vehicle noise, but also including aircraft noise and rail noise. Hybrid vehicles for road use are the first widely sold automobiles in 100 years to achieve significant noise source reduction. Poor urban planning may also give rise to noise pollution, since juxtaposition of industrial to residential land uses, for example, often results in adverse consequences for the residential acoustic environment.

Besides transportation noise, other prominent sources are office equipment, factory machinery, appliances, power tools, lighting hum and audio entertainment systems. With the popularity of digital audio player devices, individuals in a noisy area might increase the volume in order to drown out ambient sounds. Construction equipment also produces noise pollution.

Noise from recreational off-highway vehicles (OHVs) is becoming a serious problem in rural areas. ATVs, also known as quads or four wheelers, have increased in popularity and are joining the traditional two wheeled dirt motorcycles for off-road riding.

The noise from ATV machines is quite different from that of the traditional dirt bike. The ATVs have large bore, four stroke engines that produce a loud throaty growl that will carry further due to the lower frequencies involved. The traditional two stroke engines on dirt bikes have gotten larger and, while they have higher frequencies, they still can propagate the sound for a mile or more. The noise produced by these vehicle is particularly disturbing due to the wide variations in frequency and volume.

Recreational off-road vehicles are generally not required to be registered and the control of the noise they emit is absent in most communities. However, there is a growing awareness that operation of these machines can seriously degrade the quality of life of those within earshot of the noise and some communities have enacted regulations, either by imposing limits on the sound or through land use laws. Rider organizations are also beginning to recognize the problem and are enlightening members as to future restrictions on riding if noise is not curtailed.

Human health

Main article: Noise health effects

Principal noise health effects are both health and behavioral in nature. The following discussion refers to sound levels that would be present within 30 to 150 meters from a moderately busy highway.

Hearing

The mechanism for chronic exposure to noise leading to hearing loss is well established. The elevated sound levels cause trauma to the cochlear structure in the inner ear, which gives rise to irreversible hearing loss. The pinna (visible portion of the human ear) combined with the middle ear amplifies sound levels by a factor of 20 when sound reaches the inner ear. In Rosen's seminal work on serious health effects regarding hearing loss and coronary artery disease, one of his findings derived from tracking Maaban tribesmen, who were insignificantly exposed to transportation or industrial noise. This population was systematically compared by cohort group to a typical U.S. population. The findings proved that aging is an almost insignificant cause of hearing loss, which instead is associated with chronic exposure to moderately high levels of environmental noise.

Cardiovascular health

High noise levels can contribute to Cardiovascular effects and exposure to moderately high (e.g. above 70 dBA) during a single eight hour period causes a statistical rise in blood pressure of five to ten mmHg; a clear and measurable increase in stress ^[1]; and vasoconstriction leading to the increased blood pressure noted above as well as to increased incidence of coronary artery disease.

Annoyance

Though it pales in comparison to the health effects noted above, noise pollution constitutes a significant factor of annoyance and distraction in modern artificial environments:

1. The meaning listeners attribute to the sound influences annoyance, so that, if listeners dislike the noise content, they are annoyed.
2. If the sound causes activity interference, noise is more likely to annoy (for example, sleep disturbance)
3. If listeners feel they can control the noise source, the less likely the noise will be annoying.
4. If listeners believe that the noise is subject to third party control, including police, but control has failed, they are more annoyed.
5. The inherent unpleasantness of the sound causes annoyance. What is music to one is noise to another.
6. Contextual sound. If the sound is appropriate for the activity it is in context. If one is at a race track the noise is in context and the psychological effects are absent. If one is at an outdoor picnic the race track noise will produce adverse psychological and physical effects.

A 2005 study by Spanish researchers found that in urban areas households are willing to pay approximately four euros per decibel per year for noise reduction^[2].

Environment

Noise pollution can also be harmful to animals. High noise levels may interfere with the natural cycles of animals, including feeding behavior, breeding rituals and migration paths. The most significant impact of noise to animal life is the systematic reduction of usable habitat, which in the case of endangered species may be an important part of the path to extinction. Perhaps the most sensational damage caused by noise pollution is the death of certain species of beaked whales, brought on by the extremely loud (up to 200 decibels) sound of military SONAR.