noise

Noise is random or irregular disturbance that degrades the clarity or accuracy of a signal. The term is used across disciplines to describe unwanted fluctuations that obscure information. In everyday language it refers to audible sound, while in engineering it denotes undesired random variations in measurements or electrical signals.

Acoustic noise encompasses environmental sounds perceived as unwanted, such as traffic or industrial clatter. It is typically measured by sound pressure level in decibels (dB). Chronic exposure contributes to health effects and nuisance; policies address noise pollution in urban planning and workplace safety.

In electronics and instrumentation, noise refers to random fluctuations that add to a signal. Common sources include thermal noise generated by resistors, shot noise from discrete charge carriers, flicker or 1/f noise, and burst noise. Noise is often characterized by its power spectral density and by the signal-to-noise ratio (SNR) or noise floor of a system.

Noise can be categorized by spectral properties. White noise contains equal power per frequency interval, while pink noise has more energy at lower frequencies (inverse with frequency), and brown (red) noise decreases even more steeply. These models help in testing and in audio synthesis and hearing research.

Mitigation strategies aim to reduce noise impact, including shielding, careful circuit design, filtering, averaging, and dithering. Standards and regulations govern permissible noise levels in environments such as workplaces and residential areas. Understanding noise characteristics supports measurement, communication, and perception sciences.