- Ambient noise level
In atmospheric sound transmission or
noise pollution, ambient noise level is the sound pressure level at a given location, normally specified as a reference level to study a new intrusive sound source.
Ambient sound levels are often measured in order to map sound conditions over a spatial regime to understand their variation with locale. In this case the product of the investigation is a sound level contour map. Alternatively ambient noise levels may be measured to provide a reference point for analyzing an intrusive sound to a given environment. For example, sometimes
aircraft noiseis studied by measuring ambient sound without presence of any overflights, and then studying the noise addition by measurement or computer simulationof overflight events. Or roadway noiseis measured as ambient sound, prior to introducing a hypothetical noise barrierintended to reduce that ambient noise level.
noise levelis measured with a sound level meter. It is usually measured in dB above a reference pressure level of 0.00002 Pa, "i.e.," 20 μPa (micropascals) in SI units. A pascal is a newton per square meter. The centimeter-gram-second systemof units, the reference level for measuring ambient noise level is 0.0002 dyn/cm2. Most frequently ambient noise levels are measured using a frequency weighting filter, the most common being the A-weightingscale, such that resulting measurements are denoted dBA, or decibels on the A-weightingscale.
Ambient noise level is sometimes called "background noise level", "reference sound level" or "room noise level".
Noise health effects
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