# 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.

## 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
• 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 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