Noise (spectral phenomenon)

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

Acoustic noise 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.

In transportation

 * Aircraft noise
 * Jet noise, caused by high-velocity jets and turbulent eddies
 * Noise and vibration on maritime vessels
 * Noise, vibration, and harshness, quality criteria for vehicles
 * Traffic noise, including roadway noise and train noise

Other acoustic noise

 * Acoustic noise, technical term for any sound, even deliberate
 * Artificial noise, in spectator sports
 * Background noise, in acoustics, any sound other than the monitored one
 * Comfort noise, 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, that affects negatively the quality of life

Noise in biology

 * Cellular noise, in biology, random variability between cells
 * Developmental noise, variations among living beings with the same genome
 * Neuronal noise, in neuroscience
 * Synaptic noise, in neuroscience
 * Transcriptional noise, 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, created by interpolation of a lattice of pseudorandom gradients
 * Perlin noise, a type of gradient noise developed in 1983
 * Simplex noise, a method for constructing an n-dimensional noise function comparable to Perlin noise
 * Simulation noise, 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, an alternative to Perlin noise which reduces problems of aliasing and detail loss
 * Worley noise, a noise function introduced by Steven Worley in 1996

Noise in electronics and radio

 * Noise (signal processing), various types of interference
 * Noise (electronics), related to electronic circuitry
 * Ground noise, appearing at the ground terminal of audio equipment
 * Image noise, related to digital photography
 * Noise (radio), interference related to radio signals
 * Atmospheric noise, radio noise caused by lightning
 * Cosmic noise, radio noise from outside the Earth's atmosphere
 * Noise (video), "snow" on video or television pictures

Noise in mathematics

 * Any one of many statistical types or colors of noise, such as
 * White noise, which has constant power spectral density
 * Gaussian noise, with a probability density function equal to that of the normal distribution
 * Pink noise, with spectral density inversely proportional to frequency
 * Brownian noise or "brown" noise, with spectral density inversely proportional to the square of frequency
 * Pseudorandom noise, in cryptography, artificial signal that can pass for random
 * Statistical noise, a colloquialism for recognized amounts of unexplained variation in a sample
 * Shot noise, noise which can be modeled by a Poisson process
 * Noise-based logic, where logic values are different stochastic processes
 * Noise print, a statistical signature of ambient noise, used in its suppression

Other types of noise

 * Electrochemical noise, electrical fluctuations in electrolysis, corrosion, etc.
 * Phonon noise, in materials science
 * Seismic noise, random tremors of the ground

Measures of noise intensity

 * Noise figure, the ratio of the output noise power to attributable thermal noise
 * Ambient noise level, the background sound pressure level at a given location
 * Noise power, with several related meanings
 * Noise spectral density, No measured in Watt/Hertz
 * Noise temperature, temperature that would produce equivalent semiconductor noise