Noise (spectral phenomenon)

Noise refers to many types of random or unwanted signals, most commonly acoustic noise, but also including the following:

Acoustic noise

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

• Noise (acoustic), 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
• 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, N_o measured in Watt/Hertz
• Noise temperature, temperature that would produce equivalent semiconductor noise

See also

• Noise (disambiguation)