Noise is unwanted sound judged to be unpleasant, lou

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Noise From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about noise as an unwanted acoustic phenomenon. For the general signal phenomenon, see Noise (spectral phenomenon). For other uses, see Noise (disambiguation). NASA researchers at Glenn Research Center conducting tests on aircraft engine noise in 1967 Noise is unwanted sound judged to be unpleasant, loud or disruptive to hearing. From a physics standpoint, noise is indistinguishable from sound, as both are vibrations through a medium, such as air or water. The difference arises when the brain receives and perceives a sound.[1][2] In experimental sciences, noise can refer to any random fluctuations of data that hinders perception of an expected signal.[3][4] Acoustic noise is any sound in the acoustic domain, either deliberate (e.g., music or speech) or unintended. In contrast, noise in electronics may not be audible to the human ear and may require instruments for detection.[5] In audio engineering, noise can refer to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as a hiss. This signal noise is commonly measured using A-weighting[6] or ITU-R 468 weighting.[7] Contents [hide] 1 Measurement 2 Recording and reproduction 3 White noise 4 Environmental noise 5 Regulation of noise 5.1 United States 5.1.1 Noise in the workplace 5.2 Europe 6 Health effects from noise 6.1 Prevention 7 Literary views 8 See also 9 References 10 Further reading 11 External links Measurement[edit] Sound is measured based on the amplitude and frequency of a sound wave. Noise is most commonly discussed in terms of decibels (dB), the measure of loudness, or intensity of a sound; this measurement describes the amplitude of a sound wave. On the other hand, pitch describes the frequency of a sound and is measured in hertz (Hz).[8] Recording and reproduction[edit] Main article: Sound recording and reproduction In audio, recording, and broadcast systems, audio noise refers to the residual low-level sound (four major types: hiss, rumble, crackle, and hum) that is heard in quiet periods of program. This variation from the expected pure sound or silence can be caused by the audio recording equipment, the instrument, or ambient noise in the recording room.[9] In audio engineering it can refer either to the acoustic noise from loudspeakers or to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as 'hiss'. This signal noise is commonly measured using A-weighting or ITU-R 468 weighting Noise is often generated deliberately and used as a test signal for audio recording and reproduction equipment. White noise[edit] Main article: White noise White Noise Menu 0:00 Problems playing this file? See media help. White noise is energy randomly spread across a wide frequency band containing all notes from high to low. It is called "white" noise as it is analogous to "white" light which contains all the colors of the visible spectrum.[10] Environmental noise[edit] Main article: Environmental noise Environmental noise is the accumulation of all noise present in a specified environment. The principal sources of environmental noise are surface motor vehicles, aircraft, trains and industrial sources.[11] These noise sources expose millions of people to noise pollution that creates not only annoyance, but also significant health consequences such as elevated incidence of hearing loss and cardiovascular disease.[12] There are a variety of mitigation strategies and controls available to reduce sound levels including source intensity reduction, land use planning strategies, noise barriers and sound baffles, time of day use regimens, vehicle operational controls and architectural acoustics design measures. Regulation of noise[edit] Main article: Noise regulation Certain geographic areas or specific occupations may be at a higher risk of being exposed to constantly high levels of noise; in order to prevent negative health outcomes, regulations may be set. Noise regulation includes statutes or guidelines relating to sound transmission established by national, state or provincial and municipal levels of government. Environmental noise is governed by laws and standards which set maximum recommended levels of noise for specific land uses, such as residential areas, areas of outstanding natural beauty, or schools. These standards usually specify measurement using a weighting filter, most often A-weighting.[13][14] United States[edit] In 1972, the Noise Control Act was passed to promote a healthy living environment for all Americans, where noise does not pose a threat to human health. This policy's main objectives were: (1) establish coordination of research in the area of noise control, (2) establish federal standards on noise emission for commercial products, and (3) promote public awareness about noise emission and reduction.[15][16] The Qui