Noises

Noises are unwanted sounds or random fluctuations that interfere with perception or signaling. In everyday language noise refers to any sound judged to be undesired or intrusive. In engineering, noise describes random or unpredictable fluctuations that obscure a desired signal, such as electronic noise in a sensor or communications channel. Both senses share the idea of intruding, uninformative, or unpleasant content.

Acoustic noise is produced by many sources: traffic, machinery, construction, crowd noise, wind, and weather. Indoor environments may have appliances, HVAC systems, and architectural echoes. Ambient noise is the background sound in a given setting. Noise is often characterized by its spectrum: broadband noise contains energy across a wide range of frequencies, while tonal or impulsive noises have distinct components.

Measurement and terminology involve several concepts. Sound pressure level is measured in decibels (dB). Human hearing sensitivity varies with frequency; A-weighting is commonly used for evaluating annoyance. The signal-to-noise ratio expresses the relative level of the desired signal to background noise. In electronics, noise sources include thermal noise, shot noise, flicker noise, and quantization noise. White noise has equal energy per frequency, pink noise has equal energy per octave, and brown noise decreases with frequency.

Effects and mitigation are central concerns. Exposure to high noise levels can cause hearing loss, tinnitus, sleep disturbance, and increased stress. Mitigation includes engineering controls, sound insulation, urban planning, noise barriers, time-of-day restrictions, and personal protective equipment. Noise-cancelling technologies and acoustic masking can reduce perceived noise in certain contexts.

In broader use, noises appear in music and art, but in scientific contexts they are distinguished from meaningful signals. In data analysis, noise can obscure patterns and must be modeled or filtered.