Noise pollution
Noise pollution (or environmental noise in technical venues) is displeasing human or machine created sound that disrupts the environment. The dominant form of noise pollution is from transportation sources, principally motor vehicles. The word "noise" comes from the Latin word nausea meaning "seasickness", or from a derivative (perhaps Latin noxia) of Latin noceo = "I do harm", referring originally to nuisance noise.

# Sources of noise
The overarching source of most noise worldwide is generated by transportation systems, principally motor vehicle noise, but also including aircraft noise and rail noise. Hybrid vehicles are the first innovation within the last 100 years to achieve significant widespread 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. Furthermore, 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 vehicles has become a serious problem in rural areas. ATVs, also known as quads, have increased in popularity and are joining the traditional two wheeled dirt motorcycles for off-road riding.
The noise produced by these vehicles is particularly disturbing due to the wide variations in frequency and volume.

# Human health
Principal noise health effects are both health and behavioral in nature. The following discussion refers to sound levels that are present within 30 to 150 meters from a moderately busy highway. Sound is a particular auditory impression perceived by the sense of hearing. The presence of unwanted sound is called noise pollution. This unwanted sound can seriously damage and affect physiological and psychological health. For instance, noise pollution can cause annoyance and aggression, hypertension, high stress levels, tinnitus, hearing loss, and other harmful effects depending on the level of sound, or how loud it is.
Furthermore, stress and hypertension are the leading causes to health problems, whereas tinnitus can lead to forgetfulness, severe depression and at times panic attacks.

## 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. A very loud sound in a particular frequency range can damage the cochlea's hair cells that respond to that range thereby reducing the ear's ability to hear those frequencies in the future. However, loud noise in any frequency range has deleterious effects across the entire range of human hearing.
The outer ear (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, 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 levels during a single eight hour period causes a statistical rise in blood pressure of five to ten a clear and measurable increase in stress 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:
- The meaning listeners attribute to the sound influences annoyance, so that, if listeners dislike the noise content, they are annoyed. What is music to one is noise to another.
- If the sound causes activity interference, noise is more likely to annoy (for example, sleep disturbance)
- If listeners feel they can control the noise source, the noise is less likely to be annoying.
- If listeners believe that the noise is subject to third-party control, including police, but control has failed, they are more annoyed.
- The inherent unpleasantness of the sound causes annoyance.
- 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.

# Environment
Noise and other loud sounds can have a detrimental effect on animals by causing stress,
increasing risk of mortality by changing the delicate balance in predator/prey detection and
avoidance, and by interfering with their use of sounds in communication especially in relation to
reproduction and in navigation. Very significantly, acoustic overexposure can lead to temporary
-r permanent loss of hearing.

## Habitat reduction
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 beached whales, brought on by the extremely loud (up to 200 decibels) sound of military sonar.

## Lombard vocal response
Noise also makes species communicate louder, which is called Lombard vocal response. Scientists and researchers have conducted experiments that show whales' song length is longer when submarine-detecters are on. If creatures don't "speak" loud enough, their voice will be masked by anthropogenic sounds. These unheard voices might be warnings, finding of prey, or preparations of net-bubbling. When one species begins speaking louder, it will mask other species' voice, causing the whole ecosystem to eventually speak louder.

## Other habit changes
Ships may be mistaken by creatures for their predator and of course, either protect themselves, attack, or run away. If they attack, humans might have financial loss, but running away will have an even more deadly result. After they run away several times, it will become part of its habit and start ignoring it. When their natural predators come, they will stay and think that it's the boat.
Zebra finches become less faithful to their partners when exposed to traffic noise. This could alter a population's evolutionary trajectory by selecting "sexy" traits, sapping resources normally devoted to other activities and thus lead to profound genetic and evolutionary consequences.

# Mitigation and control of noise
There is also technology that has been applied with the aim of mitigating or containing noise as much as possible, provided that it has a sufficiently localized source.
- Roadway noise is the most widespread environmental component of noise pollution worldwide. There are a variety of effective strategies for mitigating adverse sound levels including: use of noise barriers, limitation of vehicle speeds, alteration of roadway surface texture, limitation of heavy duty vehicles, use of traffic controls that smooth vehicle flow to reduce braking and acceleration, innovative tire design and other methods. Thousands of case studies in the U.S. alone have been documented starting in 1970, indicating substantial improvement in roadway planning and design. The most important factor in applying these strategies is a computer model for roadway noise, that is capable of addressing local topography, meteorology, traffic operations and hypothetical mitigation. Costs of building in mitigation is often quite modest, provided these solutions are sought in the planning stage of a roadway project.
- Aircraft noise can be reduced to some extent by design of quieter jet engines, which was pursued vigorously in the 1970s and 1980s. This strategy has brought limited but noticeable reduction of urban sound levels. Reconsideration of operations, such as altering flight paths and time of day runway use, have demonstrated significant benefits for residential populations near airports. FAA sponsored residential retrofit (insulation) programs initiated in the 1970s has also enjoyed widespread success in reducing interior residential noise in thousands of affected residences across the United States.
- Exposure of Industrial noise on workers has the longest history of scientific study, having been addressed since the 1930s. This scientific studies have emphasized redesign of industrial equipment, shock mounting assemblies and physical barriers in the workplace. Innovations have had considerable success; however, the costs of retrofitting existing systems is often rather high.

# Legal status
Governments up until the 1970s viewed noise as a "nuisance" rather than an environmental problem. In the United States there are federal standards for highway and aircraft noise; states and local governments typically have very specific statutes on building codes, urban planning and roadway development. In Canada and the EU there are few national, provincial, or state laws that protect against noise.
Noise laws and ordinances vary widely among municipalities and indeed do not even exist in some cities. An ordinance may contain a general prohibition against making noise that is a nuisance, or it may set out specific guidelines for the level of noise allowable at certain times of the day and for certain activities.
Most city ordinances prohibit sound above a threshold intensity from trespassing over property line at night, typically between 10 p.m. and 6 a.m., and during the day restricts it to a higher decibel level; however, enforcement is uneven. Many municipalities do not follow up on complaints. Even where a municipality has an enforcement office, it may only be willing to issue warnings, since taking offenders to court is expensive.
Many conflicts over noise pollution are handled by negotiation between the emitter and the receiver.   Escalation procedures vary by country, and may include action in conjunction with local authorities, in particular the police. Noise pollution often persists because only five to ten percent of people affected by noise will lodge a formal complaint. Many people are not aware of their legal right to quiet and do not know how to register a complaint.