Noise refers to many types of random, troublesome, problematic, or unwanted

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

s. Acoustic

noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...

may mar aesthetic experience, such as attending a concert hall. It may also be a medical issue inherent in the biology of hearing. In technology, noise is unwanted signals in a device or apparatus, commonly of an electrical nature. The nature of noise is much studied in mathematics and is a prominent topic in statistics. This article provides a survey of specific topics linked to their primary articles.

Acoustic noise

{{main, Noise

In transportation

Aircraft noise Aircraft noise pollution refers to noise produced by aircraft in flight that has been associated with several negative stress-mediated health effects, from sleep disorders to cardiovascular ones. Governments have enacted extensive controls that a ...

Jet noise In aeroacoustics, jet noise is the field that focuses on the noise generation caused by high-velocity jets and the turbulent eddies generated by shearing flow. Such noise is known as broadband noise and extends well beyond the range of human hear ...

, caused by high-velocity jets and turbulent eddies *

Noise and vibration on maritime vessels Noise and vibration on maritime vessels are not the same but they have the same origin and come in many forms. The methods to handle the related problems are similar, to a certain level, where most shipboard noise problems are reduced by controllin ...

Noise, vibration, and harshness Noise, vibration, and harshness (NVH), also known as noise and vibration (N&V), is the study and modification of the noise and vibration characteristics of vehicles, particularly cars and trucks. While noise and vibration can be readily measured, ...

, quality criteria for vehicles *Traffic noise, including

roadway noise Roadway noise is the collective sound energy emanating from motor vehicles. It consists chiefly of road surface, tire, engine/transmission, aerodynamic, and braking elements. Noise of rolling tires driving on pavement is found to be the biggest ...

and

train noise Train noise is vehicle noise created by trains. Noises may be heard inside the train and outside. Subway systems, light rail transit and freight trains can send loud train noise into neighborhoods. Organizations such as the World Health Organi ...

Other acoustic noise

Acoustic noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...

, technical term for any sound, even deliberate *

Artificial noise Artificial noise is a wave or vibration, audible, electromagnetic, or other signal, generated by a human source. Usage The purpose of generating artificial noise, whether intentional or not, may vary, depending on what is considered noise in a p ...

, in spectator sports *

Background noise Background noise or ambient noise is any sound other than the sound being monitored (primary sound). Background noise is a form of noise pollution or interference. Background noise is an important concept in setting noise levels. Background n ...

, in acoustics, any sound other than the monitored one *

Comfort noise Comfort noise (or comfort tone) is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines. So ...

, used in telecommunications to fill silent gaps * Grey noise, random noise with a psychoacoustic adjusted spectrum * Industrial noise, relevant to hearing damage and industrial hygiene *

Noise pollution Noise pollution, also known as environmental noise or sound pollution, is the propagation of noise with ranging impacts on the activity of human or animal life, most of them are harmful to a degree. The source of outdoor noise worldwide is main ...

, that affects negatively the quality of life

Noise in biology

Cellular noise Cellular noise is random variability in quantities arising in cellular biology. For example, cells which are genetically identical, even within the same tissue, are often observed to have different expression levels of proteins, different sizes and ...

, in biology, random variability between cells *

Developmental noise Developmental noise is a concept within developmental biology in which the phenotype varies between individuals even though both the genotypes and the environmental factors are the same for all of them. Contributing factors include stochastic gene ...

, variations among living beings with the same genome * Neuronal noise, in neuroscience *

Synaptic noise Synaptic noise refers to the constant bombardment of synaptic activity in neurons. This occurs in the background of a cell when potentials are produced without the nerve stimulation of an action potential, and are due to the inherently random natur ...

, in neuroscience *

Transcriptional noise Transcriptional noise is a primary cause of the variability (noise) in gene expression occurring between cells in isogenic populations (see also cellular noise) . A proposed source of transcriptional noise is transcriptional bursting although oth ...

, in biochemistry, errors in genetic transcription

Noise in computer graphics

''Noise'' in computer graphics refers to various pseudo-random functions used to create textures, including: *

Gradient noise Gradient noise is a type of noise commonly used as a procedural texture primitive in computer graphics. It is conceptually different, and often confused with value noise. This method consists of a creation of a lattice of random (or typically pse ...

, created by interpolation of a lattice of pseudorandom gradients **

Perlin noise Perlin noise is a type of gradient noise developed by Ken Perlin. History Ken Perlin developed Perlin noise in 1983 as a result of his frustration with the "machine-like" look of computer-generated imagery (CGI) at the time. He formally descr ...

, a type of gradient noise developed in 1983 *

Simplex noise Simplex noise is the result of an ''n''-dimensional noise function comparable to Perlin noise ("classic" noise) but with fewer directional artifacts and, in higher dimensions, a lower computational overhead. Ken Perlin designed the algorithm in ...

, a method for constructing an ''n''-dimensional noise function comparable to Perlin noise *

Simulation noise Simulation noise is a function that creates a divergence-free vector field. This signal can be used in artistic simulations for the purposes of increasing the perception of extra detail. The function can be calculated in three dimensions by divi ...

, a function that creates a divergence-free field * Value noise, created by interpolation of a lattice of pseudorandom values; differs from gradient noise *

Wavelet noise Wavelet noise is an alternative to Perlin noise which reduces the problems of aliasing and detail loss that are encountered when Perlin noise is summed into a fractal In mathematics, a fractal is a geometric shape containing detailed stru ...

, an alternative to Perlin noise which reduces problems of aliasing and detail loss *

Worley noise Worley noise is a noise function introduced by Steven Worley in 1996. In computer graphics it is used to create procedural textures, i.e. textures that are created automatically with arbitrary precision and do not have to be drawn by hand. Worle ...

, a noise function introduced by Steven Worley in 1996

Noise in electronics and radio

Noise (signal processing) In signal processing, noise is a general term for unwanted (and, in general, unknown) modifications that a signal (signal processing), signal may suffer during capture, storage, transmission, processing, or conversion. Vyacheslav Tuzlukov (2010 ...

, various types of interference **

Noise (electronics) In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics, and central to the ...

, related to electronic circuitry ***

Ground noise In an electrical system, a ground loop or earth loop occurs when two points of a circuit are intended to have the same ground reference potential but instead have a different potential between them. This is typically caused when enough curren ...

, appearing at the ground terminal of audio equipment **

Image noise Image noise is random variation of brightness or color information in images, and is usually an aspect of electronic noise. It can be produced by the image sensor and circuitry of a Image scanner, scanner or digital camera. Image noise can also ...

, related to digital photography **

Noise (radio) In radio reception, radio noise is unwanted random radio frequency electrical signals, fluctuating voltages, always present in a radio receiver in addition to the desired radio signal. Radio noise near in frequency to the radio signal being receive ...

, interference related to radio signals ***

Atmospheric noise Atmospheric noise is radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorms. On a worldwide scale, there are about 40 lightning flashes per second – ≈3.5 million lightning discharges ...

, radio noise caused by lightning ***

Cosmic noise Cosmic noise, also known as galactic radio noise, is not actually sound, but a physical phenomenon derived from outside of the Earth's atmosphere. It can be detected through a radio receiver, which is an electronic device that receives radio waves ...

, radio noise from outside the Earth's atmosphere **

Noise (video) Noise, commonly known as static, white noise, static noise, or snow, in analog video and television, is a random dot pixel pattern of static displayed when no transmission signal is obtained by the antenna receiver of television sets and other d ...

, "snow" on video or television pictures

Noise in mathematics

*Any one of many statistical types or

colors of noise In audio engineering, electronics, physics, and many other fields, the color of noise or noise spectrum refers to the power spectrum of a noise signal (a signal produced by a stochastic process). Different colors of noise have significantly ...

, such as **

White noise In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used, with this or similar meanings, in many scientific and technical disciplines, ...

, which has constant power spectral density **

Gaussian noise Gaussian noise, named after Carl Friedrich Gauss, is a term from signal processing theory denoting a kind of signal noise that has a probability density function (pdf) equal to that of the normal distribution (which is also known as the Gaussia ...

, with a probability density function equal to that of the normal distribution **

Pink noise Pink noise or noise is a signal or process with a frequency spectrum such that the power spectral density (power per frequency interval) is inversely proportional to the frequency of the signal. In pink noise, each octave interval (halving ...

, with spectral density inversely proportional to frequency **

Brownian noise ] In science, Brownian noise, also known as Brown noise or red noise, is the type of signal noise produced by Brownian motion, hence its alternative name of random walk noise. The term "Brown noise" does not come from the color, but after ...

or "brown" noise, with spectral density inversely proportional to the square of frequency *

Pseudorandom noise In cryptography, pseudorandom noise (PRN) is a signal similar to noise which satisfies one or more of the standard tests for statistical randomness. Although it seems to lack any definite pattern, pseudorandom noise consists of a deterministic s ...

, in cryptography, artificial signal that can pass for random *

Statistical noise In statistics, the fraction of variance unexplained (FVU) in the context of a regression task is the fraction of variance of the regressand (dependent variable) ''Y'' which cannot be explained, i.e., which is not correctly predicted, by the e ...

, a colloquialism for recognized amounts of unexplained variation in a sample *

Shot noise Shot noise or Poisson noise is a type of noise which can be modeled by a Poisson process. In electronics shot noise originates from the discrete nature of electric charge. Shot noise also occurs in photon counting in optical devices, where shot ...

, noise which can be modeled by a Poisson process *

Noise-based logic Noise-based logic (NBL) is a class of multivalued deterministic logic schemes, developed in the twenty-first century, where the logic values and bits are represented by different realizations of a stochastic process. The concept of noise-based log ...

, where logic values are different stochastic processes *

Noise print A noise print is part of a technique used in noise reduction. A noise print is commonly used in audio mastering to help reduce the effects of unwanted noise from a piece of audio. In this case, the noise print would be a recording of the ambient no ...

, a statistical signature of ambient noise, used in its suppression

Other types of noise

* Electrochemical noise, electrical fluctuations in electrolysis, corrosion, etc. *

Phonon noise Phonon noise, also known as thermal fluctuation noise, arises from the random exchange of energy between a thermal mass and its surrounding environment. This energy is quantized in the form of phonons. Each phonon has an energy of order k_\textT, w ...

, in materials science *

Seismic noise In geophysics, geology, civil engineering, and related disciplines, seismic noise is a generic name for a relatively persistent vibration of the ground, due to a multitude of causes, that is often a non-interpretable or unwanted component of signal ...

, random tremors of the ground

Measures of noise intensity

Noise figure Noise figure (NF) and noise factor (''F'') are figures of merit that indicate degradation of the signal-to-noise ratio (SNR) that is caused by components in a signal chain. These figures of merit are used to evaluate the performance of an amplifier ...

, the ratio of the output noise power to attributable thermal noise *

Ambient noise level In atmospheric sounding and noise pollution, ambient noise level (sometimes called background noise level, reference sound level, or room noise level) is the background sound pressure level at a given location, normally specified as a reference l ...

, the background sound pressure level at a given location *

Noise power In telecommunication, the term noise power has the following meanings: # The measured total noise in a given bandwidth at the input or output of a device when the signal is not present; the integral of noise spectral density over the bandwidth # T ...

, with several related meanings *

Noise spectral density In communications, noise spectral density (NSD), noise power density, noise power spectral density, or simply noise density (''N''0) is the power spectral density of noise or the noise power per unit of bandwidth. It has dimension of power over fre ...

, ''N''_o measured in Watt/Hertz *

Noise temperature In electronics, noise temperature is one way of expressing the level of available noise power introduced by a component or source. (This is to be distinguished from Temperature Noise in Thermodynamics or Principal Interferrometric Analysis Over C ...

, temperature that would produce equivalent semiconductor noise