Environmental noise

Noise is frequently described as 'unwanted sound'. Within this context, environmental noise is generally present in some form in all areas of human, animal, or environmental activity. The effects in humans of exposure to environmental noise may vary from emotional to physiological and psychological. Noise at low levels is not necessarily harmful. Environmental noise can also convey a sense of liveliness in an area, which can be desirable. However, the adverse effects of noise exposure (i.e. noise pollution) could include: interference with speech or other 'desired' sounds, annoyance, sleep disturbance, anxiety, hearing damage and stress-related cardiovascular health problems. As a result, environmental noise is studied, regulated, and monitored by many governments and institutions around the world. This creates a number of different occupations. The basis of all decisions is supported by the objective and accurate measurement of noise. Noise is measured in decibels (dB) using a pattern-approved sound level meter. The measurements are typically taken over a period of weeks, in all weather conditions. Noise from transportation is typically emitted by machinery (e.g. the engine or exhaust) and aerodynamic noise (see aerodynamics and aircraft noise) caused by the compression and friction in the air around the vessel during motion. Environmental noise from the railway specifically is variable depending on the speed and quality of the tracks used for transportation. Industrial and recreational noise could be generated by a multitude of different sources and processes. Industrial noise can be generated by factories and plants (i.e., product fabrication or assembly), power generation (hydroelectricity or wind turbines), construction activities, or agricultural and meat processing facilities. Sources of recreational noise vary widely but they can include music festivals, shooting ranges, sporting events, car racing, woodworking, pubs, people's activities on the street, etc. Sound propagation outdoors is subject to meteorological effects (e.g. wind, temperature) that affect the distance, speed, and direction with which environmental noise travels from a source to a listener. Noise and quality of life are correlated. The increase of environmental noise, especially for those living near railways and airports, has created conflict. Getting adequate and quality sleep is difficult for those who live in areas of high noise exposure. When the body is at rest, noise stimuli is continually being presented in the environment. The body responds to these sounds which can negatively affect sleep.