noise

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A term used by analysts of time series data to describe random fluctuations that may obscure the true signal. A sequence of errors, in successive observations, that consists of independent random values from a normal distribution with zero mean is termed white noise.

For more information on noise, visit Britannica.com.

(1) Extraneous, unwanted signals that invade an electrical or optical system. In electronics, noise can come from strong electrical or magnetic signals in nearby lines, from poorly fitting electrical contacts and from power line spikes. In optics, noise comes from the stray reflections of light that emanate from the various components in the optical system. See signal-to-noise ratio and noise cancellation.

(2) Distortions in analog and digital video images that are caused by a variety of circumstances. The silver grains in the original film create granular noise. Electronic circuits create Gaussian noise. Drop outs and bit errors in digital tapes create impulse noise, and the digitization process creates quantization noise. See Gaussian noise, dynamic noise reduction and artifact.

(3) Distortions in a still image caused by variations in the pixels in the CCD or CMOS sensor. See digital camera.

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noun

1. Sounds or a sound, especially when loud, confused, or disagreeable: babel, clamor, din, hubbub, hullabaloo, pandemonium, racket, rumpus, tumult, uproar. See sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.
2. The sensation caused by vibrating wave motion that is perceived by the organs of hearing: sonance, sound¹. See sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.

verb

1. To make (information) generally known: advertise, blaze², blazon, broadcast, bruit, circulate, disseminate, promulgate, propagate, spread. Idioms: spread far and wide, spread the word. See knowledge/ignorance.
2. To engage in or spread gossip: blab, gossip, rumor, talk, tattle, tittle-tattle, whisper. Idioms: tell tales, tell tales out of school. See words.

Definition: sound which is loud, not harmonious
Antonyms: silence

Sound is an essential form of human communication. However, unwanted sounds, or noise, can lead to a variety of medical problems, including deafness and elevated blood pressure; there is also evidence for an increased pulse rate. There is some evidence suggesting that environmental noise may affect the learning ability of children.

Sound waves are generated by vibrations moving through the air, and they are perceived through a complex interaction of vibrations hitting the inner ear. External vibrations are translated, through bones, into additional vibrations, which are then picked up by hair-like structures in the inner ear. These vibrations are further translated into neurologic signals, which are registered in the brain and received as intelligible information.

Noise can be normal sounds that get in the way of being able to perceive wanted sounds. Sound is measured in units called decibels, and the human ear is well-designed to perceive and interpret sounds at low decibel levels and across a wide spectrum of vibration. Sounds that are too loud, however, can damage the ability of the ear to make sense of what is perceived. A graphic measurement of what one can hear is called an audiogram, and hearing loss can be traced on audiograms. There is some hearing loss that is considered normal with aging, called presbycusis. Additional hearing loss and other physiological damage, may result from excessive loud noise.

There is some controversy as to what level of sound is too high, particularly in workplaces. It is thought that the maximal tolerable noise level for an eight-hour workplace exposure is about seventy-five decibels. The current allowable standard is eighty-five decibels. The standard was decreased from the previous ninety decibel level after a hard-fought battle to try and prevent a significant number of cases of hearing loss. At eighty-five decibels, hearing protection and noise monitoring becomes mandatory. There are several ways that noise can be reduced, either through changes in noise-making equipment itself, or by providing personal protective equipment to individuals who must work in noisy environments. The two basic types of personal protection are earplugs and earmuffs. Earmuffs, which can be put on and taken off more easily, are useful where the noise may be intermittent, such as at airports. Earplugs are more practical for people who spend considerable continuous periods of time in noisy environments.

In addition to noisy workplace environments, there are certain general environments where noise may be a particular problem. Among these are subway systems, where passengers may be intermittently exposed to high noise levels, and in communities located near airports. Over time there has been a considerable effort to diminish the noise around airports, both through the use of quieter engines and through changes in flight paths. In some extreme situations, homes have been bought and people moved out of flight paths near airports to help reduce the risk and annoyance associated with such noise.

(SEE ALSO: Hearing Disorders; Hearing Protection; Occupational Safety and Health)

Bibliography

Moller, A. G. (1992). "Noise as a Health Hazard." In Public Health and Preventive Medicine, 13th edition, eds. J. M. Last and R. M. Wallace. Norwalk, CT: Appleton and Lange.

— ARTHUR L. FRANK

Any sound which is unwanted because it is annoying, interferes with speech and hearing, or is intense enough to damage hearing.

Noise, mottling or colour-speckle interference in digital images, usually in shadow areas and at sensitivity equivalents of ISO 400 or higher. Noise levels may be related to factors such as the number of pixels in a sensor, or their configuration and architecture, or heat generated by long exposures, or the camera's processing algorithms. Sustained research by manufacturers has reduced noise, in high-end cameras, to a level at or below comparable grain in film.

— Robin Lenman

1. A term used in information theory to indicate a disturbance that does not represent any part of a message from a specified source.

2. Background stimuli (or information), which a person might or might not be aware of, but which is not directly relevant to the task in hand.

3. In signal detection theory, the random firing of the nervous system; that is background neural activity.

Price and volume fluctuations in the market that can confuse one's interpretation of market direction. Used in the context of equities, it is stock market activity caused by program trading, dividend payments or other phenomena that is not reflective of overall market sentiment. Also known as "market noise".

Investopedia Says:
In general, the shorter the time frame, the more difficult it is to separate the meaningful market movements from the noise. Noise traders attempt to take advantage of market noise by entering buy and sell transactions without the use of fundamental data.

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Unwanted electromagnetic radiation within an electrical or mechanical system.

n.

A stench in the ear. Undomesticated music. The chief product and authenticating sign of civilization.

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Quotes:

"All this talk and turmoil and noise and movement and desire is outside of the veil; within the veil is silence and calm and rest." - Bayazid Al-Bistami

"For twenty-five centuries, Western knowledge has tried to look upon the world. It has failed to understand that the world is not for the beholding. It is for hearing. It is not legible, but audible. Our science has always desired to monitor, measure, abstract, and castrate meaning, forgetting that life is full of noise and that death alone is silent: work noise, noise of man, and noise of beast. Noise bought, sold, or prohibited. Nothing essential happens in the absence of noise." - Jacques Attali

"The world is never quiet, even its silence eternally resounds with the same notes, in vibrations which escape our ears. As for those that we perceive, they carry sounds to us, occasionally a chord, never a melody." - Albert Camus

"He who sleeps in continual noise is wakened by silence." - William Dean Howells

"In antiquity there was only silence. In the nineteenth century, with the invention of the machine, Noise was born. Today, Noise triumphs and reigns supreme over the sensibility of men." - Luigi Russolo

1. a loud, harsh and objectionable sound.
2. interference in an ecological or electronic system, but insufficient to stop the system.
3. in statistics when extraneous, uncontrolled variables cause errors in the distribution of data.

• n. pollution — noise in the environment that adversely affects, in our context, the animal inhabitants. No such ill effects have been demonstrated.

• General Technology - noise: random signals, interference, or nonmanaged data
• Sound, Hearing, and Deafness - noise: sound, esp. loud, harsh, or confused one; clamor
• Drug Names and Forms - noise: Slang. heroin

This article is about noise as an unwanted phenomenon. For other uses, see Noise (disambiguation).

NASA researchers at Glenn Research Center conducting tests on aircraft engine noise in 1967

In common use, the word noise means any unwanted sound.

In physics and analog electronics, noise is a mostly unwanted random addition to a signal; it is called noise as a generalisation of the acoustic noise ("static") heard when listening to a weak radio transmission with significant electrical noise. Signal noise is heard as acoustic noise if the signal is converted into sound (e.g., played through a loudspeaker); it manifests as "snow" on a television or video image. High noise levels can block, distort, change or interfere with the meaning of a message in human, animal and electronic communication.

In signal processing or computing it can be considered random unwanted data without meaning; that is, data that is not being used to transmit a signal, but is simply produced as an unwanted by-product of other activities. "Signal-to-noise ratio" is sometimes used to refer to the ratio of useful to irrelevant information in an exchange.

In biology, many different forms of cellular noise exist, where a measurement displays substantial variance around its mean: for example, transcriptional noise describes the variability in gene activity between cells in a population.

In many cases, the special case of thermal noise arises, which sets a fundamental lower limit to what can be measured or signaled and is related to basic physical processes described by thermodynamics, some of which are expressible by simple formulae.

In some fields, noise means unwanted information or data that is not relevant to the hypothesis or theory being investigated or tested.

Contents 1 Acoustic noise 1.1 Regulation of acoustic noise 2 Use in Music 2.1 Audio noise 2.2 Acoustic noise in film sound 3 Non-acoustic noise 3.1 Electronic noise and communication channel noise 3.2 Visual noise 3.3 Vibrational noise 3.4 Noisy genes 4 See also 5 References 6 Further reading 7 External links

Acoustic noise

In relation to sound, noise is not necessarily random. Sounds, particularly loud ones, that disturb people or make it difficult to hear wanted sounds, are noise. For example, conversations of other people may be called noise by people not involved in any of them; any unwanted sound such as domesticated dogs barking, neighbours playing loud music, portable mechanical saws, road traffic sounds, or a distant aircraft in quiet countryside, is called noise.

Acoustic noise can be anything from quiet but annoying to loud and harmful. At one extreme users of public transport sometimes complain about the faint and tinny sounds emanating from the headphones or earbuds of somebody listening to a portable audio player; at the other the sound of very loud music, a jet engine at close quarters, etc. can cause permanent irreversible hearing damage.

Sound intensity follows an inverse square law with distance from the source; doubling the distance from a noise source reduces its intensity by a factor of four, or 6 dB.

Regulation of acoustic noise

Main article: Noise regulation

Noise regulation includes statutes or guidelines relating to sound transmission established by national, state or provincial and municipal levels of government. After a watershed passage of the U.S. Noise Control Act of 1972[1], the program was abandoned at the federal level, under President Ronald Reagan, in 1981 and the issue was left to local and state governments. Although the UK and Japan enacted national laws in 1960 and 1967 respectively, these laws were not at all comprehensive or fully enforceable as to address (a) generally rising ambient noise (b) enforceable numerical source limits on aircraft and motor vehicles or (c) comprehensive directives to local government.

Use in Music

Main article: Noise in music

See also: Noise music

Percussion instruments are inherently noisy by nature. Specifically, snare drums (vibrations of a circular membrane), create a very noisy wave shortly after they are struck. The double headed nature of this instrument means that the harmonics are extraordinarily complex, as between both of them, there are, theoretically, an infinite number of resonant modes, and thus harmonics. In practice, though, the sound produced is not infinitely harmonic, rather it is extremely dissonant, due to the large number of constrcting and distructing interfaces.

Audio noise

	White Noise
Problems listening to this file? See media help.

Main article: Colors of noise

In audio, recording, and broadcast systems audio noise refers to the residual low level sound (usually hiss and hum) that is heard in quiet periods of programme^{[citation needed]}.

In audio engineering it can also refer 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.

Acoustic noise in film sound

For film sound theorists and practitioners at the advent of talkies c.1928/1929, noise was non-speech sound or natural sound, and for many of them, noise (especially asynchronous use with image) was desired over the evils of dialogue synchronized to moving image. The director and critic René Clair writing in 1929 makes a clear distinction between film dialogue and film noise and very clearly suggests that noise can have meaning and be interpreted: "...it is possible that an interpretation of noises may have more of a future in it. Sound cartoons, using "real" noises, seem to point to interesting possibilities".^[1] Alberto Cavalcanti uses noise as a synonym for natural sound ^[2] and as late as 1960, Siegfried Kracauer was referring to noise as non-speech sound.^[3]

Non-acoustic noise

Electronic noise and communication channel noise

Main article: Noise (electronics)

Electronic noise exists in all circuits and devices as a result of thermal noise, also referred to as Johnson Noise. It is caused by random variations in current or voltage caused by the random movement of charge carriers (usually electrons) carrying the current as they are jolted around by thermal energy. Thermal noise can be reduced by reducing the temperature of the circuit. This phenomenon limits the minimum signal level that any radio receiver can usefully respond to, because there will always be a small but significant amount of thermal noise arising in its input circuits. This is why radio telescopes, which search for very low levels of signal from space, use front-end low-noise amplifier circuits cooled with liquid nitrogen.

There are several other sources of noise in electronic circuits such as shot noise, seen in very low-level signals where the finite number of energy-carrying particles becomes significant, or flicker noise (1/f noise) in semiconductor devices. A digitized and reconstructed analog signal is exposed to additive quantization noise.

In a communication channel, noise is an undesired random signal, often modelled as additive white gaussian noise (AWGN), that may be caused by thermal noise or electromagnetic interference (EMI) from unkown sources. Noise shold not be confused with crosstalk and other interference from other communication system transmitters. Phase or frequency modulated communication systems may suffer from phase noise due to synchronization problems and time-invariant channel conditions, caused by mobility, fading and doppler shift. Deliberate generation of communication system noise and interference is called jamming.

Visual noise

Main article: Image noise

Noise is also present in images. Electronic noise will be present in camera sensors, and the physical size of the grains of film emulsion creates visual noise. This kind of noise is referred to as "grain."

Noise is also used in the creation of 2D and 3D images by computer. Sometimes noise is added to images to hide the sudden transitions inherent in digital representation of color, known as "banding". This adding of noise is referred to as "dithering." Sometimes noise is used to create the subject matter itself. Procedural noise (such as Perlin noise) is often used to create natural-looking variation in computer generated images.

Vibrational noise

Main article: Ambient Vibrations

The Earth ground and the built environment are subjected to permanent vibrations commonly referred to as seismic noise but nowadays preferably called Ambient Vibrations. These vibrations have natural (ocean waves, wind...) and anthropogenic (traffic, machines...) origins depending on the considered frequency range. These vibrations may be disturbing for people (housing close to railway tracks...) and even cause solidian noise (acoustic noise created by particular vibrations of solids like rooms) but they are also used (recorded) to characterize the structures (civil engineering structure, underground) they are shaking in terms of dynamic properties and eventually physical properties.

Noisy genes

Main article: Cellular noise

The activity and regulation of our genes are also subject to noise. Transcriptional noise refers to the variability in gene activity between cells in genetically identical populations (even identical twins are non-identical). Noise in gene activity has tremendous consequences on cell behaviour, and must be mitigated or integrated. Noise impacts upon the effectiveness of clinical treatment, with resistance of bacteria to antibiotics demonstrably caused by non-genetic differences. Variability in gene expression may also contribute to resistance of sub-populations of cancer cells to chemotherapy. In certain contexts, such as the survival of microbes in rapidly changing stressful environments, or several types of scattered differentiation, noise may be essential.

See also

• Association of Noise Consultants
• Background noise
• Noise and vibration on maritime vessels
• Noise (music)
• Noise pollution
• Silence

References

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2011)

1. ^ Clair, René (1985). "The Art of Sound". In Weis, Elisabeth; Belton, John. Film Sound: Theory and Practice. New York: Columbia University Press. p. 92. 
2. ^ Cavalcanti, Alberto (1939). "Sound in Films". Films: A Quarterly of Discussion and Analysis (Arno Press) 1: 25. 
3. ^ Kracauer, Siegfried (1960). "Chapter 7: Dialogue and Sound". Theory of Film: The Redemption of Physical Reality. Oxford University Press. p. 102. 

Further reading

• Kosko, Bart (2006). Noise. Viking Press. ISBN 0-670-03495-9. 
• Schwartz, Hillel (2011). Making Noise: From Babel to the Big Bang & Beyond. New York: Zone Books. ISBN 978-1-935408-12-3. 

External links

Look up noise in Wiktionary, the free dictionary.

Wikiquote has a collection of quotations related to: Sound

Wikimedia Commons has media related to: Noise

• Guidelines for Community Noise, World Health Organization, 1999
• Audio Measuring Articles - Electronics
• Mohr on Receiver Noise: Characterization, Insights & Surprises
• Noise voltage - Calculation and Measuring of Thermal Noise
• Noise at work European Agency for Safety and Health at Work (EU-OSHA)
• Article "Noise Control Techniques"
• Mountain & Plains ERC: A NIOSH Education and Research Center for Occupational & Environmental Health & Safety
• US National Institute for Occupational Safety and Health, - Noise

v t e Noise (in physics and telecommunications) General Distortion Noise control Noise measurement Noise power Noise reduction Noise temperature Phase distortion Noise in... Audio Electronics Images Radio Video Class of noise Additive white Gaussian noise (AWGN) Atmospheric noise Background noise Brownian noise Burst noise Cosmic noise Flicker noise Gaussian noise Grey noise Jitter Johnson–Nyquist noise Pink noise Quantization error (or q. noise) Shot noise White noise Engineering terms Channel noise level Circuit noise level Effective input noise temperature Equivalent noise resistance Equivalent pulse code modulation noise Impulse noise (audio) Noise figure Noise floor Noise shaping Noise spectral density Phase noise Pseudorandom noise Statistical noise Ratios Carrier-to-noise ratio (C/N) Carrier-to-receiver noise density (C/kT) dBrnC Eb/N0 (energy per bit to noise density) Es/N0 (energy per symbol to noise density) Modulation error ratio (MER) Signal, noise and distortion (SINAD) Signal-to-interference ratio (S/I) Signal-to-noise ratio (S/N, SNR) Signal to noise ratio (imaging) Signal-to-noise plus interference (SNIR) Signal-to-quantization-noise ratio (SQNR) Related topics List of noise topics Colors of noise Interference (communication) Radio noise source Spectrum analyzer Thermal radiation

v t e Timbre Colors of noise · Fundamental frequency · Loudness · Microinflection · Noise · Pitch · Rustle noise · Spectral envelope · Tonality

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Dansk (Danish)
n. - larm, støj, lyd
v. tr. - udbasunere, forkynde vidt og bredt
v. intr. - larme, støje

idioms:

• make (all) the right noises    sige det, der forventes, ytre banaliteter
• noise pollution    lydforurening

Nederlands (Dutch)
lawaai, geluid, gedruis, geruis, kletsen, lawaai schoppen, ruchtbaar maken, veelbesproken zijn (negatief)

Français (French)
n. - bruit, vacarme, (Élec, Télécom) interférences, tapage
v. tr. - rendre public, ébruiter
v. intr. - rendre public, ébruiter

idioms:

• make all the right noises    se montrer complaisant
• make the right noises    se montrer complaisant
• noise pollution    nuisances sonores

Deutsch (German)
n. - Geräusch, Lärm
v. - verbreiten, viel od. laut reden

idioms:

• make all the right noises    vage sprechen
• make the right noises    vage sprechen
• noise pollution    Lärmbelästigung

Ελληνική (Greek)
n. - θόρυβος, ορυμαγδός (κν. σαματάς), κρότος, βοή, (μτφ.) πάταγος, σάλος (κν. ντόρος), ηλεκτρονικά παράσιτα
v. - κάνω βούκινο

idioms:

• make (all) the right noises    έχω όλες τις σωστές αντιδράσεις, λέω αυτά που περιμένουν να ακούσουν
• noise pollution    ηχορύπανση

Italiano (Italian)
suono, rumore, perturbazione sonora

idioms:

• make (all) the right noises    esprimersi chiaramente
• noise pollution    inquinamento acustico

Português (Portuguese)
n. - ruído (m), clamor (m), rumor (m), escândalo (m)
v. - fazer barulho, falar muito, propalar

idioms:

• make (all) the right noises    expressar algo verbalmente
• noise pollution    poluição sonora

Русский (Russian)
шум, помехи

idioms:

• make (all) the right noises    говорить то, что следует
• noise pollution    звуковые помехи

Español (Spanish)
n. - ruido, estrépito, tumulto, alboroto, interferencia
v. tr. - esparcir, rumorear, divulgar
v. intr. - hablar a gritos, gritar, meter ruido

idioms:

• make all the right noises    mostrarse francamente favorable a, hablarse mucho de una cosa
• make the right noises    mostrarse francamente favorable a, hablarse mucho de una cosa
• noise pollution    ruido dañino y molesto

Svenska (Swedish)
n. - buller, ljud, bråk, oljud, rykte
v. - sprida (ut)

中文（简体）(Chinese (Simplified))
喧闹声, 噪音, 噪声, 谣传, 喧闹

idioms:

• make (all) the right noises    随声附和
• noise pollution    噪音污染

中文（繁體）(Chinese (Traditional))
n. - 喧鬧聲, 噪音, 雜訊
v. tr. - 謠傳
v. intr. - 喧鬧

idioms:

• make (all) the right noises    隨聲附和
• noise pollution    噪音污染

한국어 (Korean)
n. - 평판, 헛소리, 소음
v. tr. - 소문 내다
v. intr. - 지껄이다, 소리를 내다

idioms:

• make (all) the right noises    광고나 이목을 끌기에 알맞게 말하다

日本語 (Japanese)
n. - 音, 騒音, 雑音

idioms:

• make (all) the right noises    気を引く
• noise pollution    騒音公害

العربيه (Arabic)
‏(الاسم) ضجيج (فعل) يحدث ضجه‏

עברית (Hebrew)
n. - ‮רעש, קול, תנודות לא-סדירות הנלוות לאות משודר‬
v. tr. - ‮פרסם, הפיץ, רחש‬
v. intr. - ‮פרסם, הפיץ, רחש‬

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