Noise
Unwanted sound measured in decibels, regulated for health and environment.
Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium; the difference arises when the brain receives and perceives a sound. Noise may also refer to a random or unintended component of an electronic signal, or to an intentionally produced random signal such as white noise or pink noise.
- Measurement unit
- Decibels (dB) for amplitude; hertz (Hz) for frequency
- Principal environmental sources
- Surface motor vehicles, aircraft, trains, industrial sources
- Key European regulation
- Environmental Noise Directive; Marine Strategy Framework Directive (MSFD)
- Occupational exposure limit (NIOSH)
- 85 dBA for 8 hours with 3-dB exchange rate
- Occupational exposure limit (OSHA)
- 90 dBA for 8 hours average
Lore & Background
Regulation of noise exists at national, state, and municipal levels. NIOSH recommends an exposure limit of 85 dBA for 8 hours with a 3-dB exchange rate, while OSHA maintains a 90 dBA average. In Europe, the Environmental Noise Directive determines exposure levels and reduces environmental noise, and the MSFD treats underwater noise as a pollutant. Health effects of noise exposure include hearing loss, high blood pressure, ischemic heart disease, sleep disturbances, and decreased school performance. Noise-induced hearing loss is permanent but preventable through engineering controls, the Buy-Quiet initiative, and hearing protection, though studies show hearing protection devices without proper selection and fit testing do not significantly reduce risk.
Reader's Guide
Noise is a pervasive environmental and occupational factor with significant implications for public health. Its measurement and regulation are grounded in physics—amplitude in decibels and frequency in hertz—but its perception and impact are subjective and physiological. The distinction between noise and desired sound is made by the brain, not by the physical wave. Regulatory frameworks in the United States and Europe aim to limit exposure, particularly in workplaces and communities, to prevent hearing loss and other health effects such as cardiovascular disease and sleep disruption. The use of A-weighting in standards reflects human hearing sensitivity. Despite regulations, noise remains the most common work-related pollutant, and prevention efforts like the Buy-Quiet initiative and Safe-In-Sound award seek to reduce risks. The legacy of noise research and regulation is a growing recognition that noise is not merely an annoyance but a measurable hazard requiring systematic control, from engineering solutions to land-use planning.
Did You Know?
- NIOSH recommends an occupational exposure limit of 85 dBA for 8 hours with a 3-dB exchange rate, while OSHA maintains a 90 dBA average.
- Underwater noise is classified as a pollutant under the European Union's Marine Strategy Framework Directive.
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