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to calculate a current situation based on existing physics, mostly when a physical measurement at a location is impractical; to predict the resulting immission levels based on a planned change, e.g. set up of a new machine; Mostly, noise calculation is part of any such planning process and may become part of the decision process for physical change
Sound exposure level (SEL) is a logarithmic measure of the sound exposure of a sound relative to a reference value. Sound exposure level, denoted L E and measured in dB , is defined by [ 1 ]
Although sound pressure and intensity differ, both can describe the level of loudness by comparing the current state to the threshold of hearing; this results in decibel units on the logarithmic scale. [12] [13] The logarithmic scale accommodates the vast range of sound heard by the human ear. Depiction of frequency weighting
Ambient noise level is measured with a sound level meter. [4] It is usually measured in dB relative to a reference pressure of 0.00002 Pa, i.e., 20 μPa (micropascals) in SI units. [5] This is because 20 μPa is the faintest sound the human ear can detect. [5] A pascal is a newton per square meter.
While 1 atm (194 dB peak or 191 dB SPL) [11] [12] is the largest pressure variation an undistorted sound wave can have in Earth's atmosphere (i. e., if the thermodynamic properties of the air are disregarded; in reality, the sound waves become progressively non-linear starting over 150 dB), larger sound waves can be present in other atmospheres ...
While describing sound in terms of sound pressure, a logarithmic conversion is usually applied and the sound pressure level is stated instead, in decibels (dB), with 0 dB SPL equal to 20 micropascals. A microphone is distinguishable by the voltage value produced when a known, constant root mean square sound pressure is applied. This is known as ...
When sound levels reach a high enough intensity, the sound, whether it is wanted or unwanted, may be damaging to hearing. [3] Environmental noise monitoring is the measurement of noise in an outdoor environment caused by transport (e.g. motor vehicles, aircraft, and trains), industry (e.g. machines) and recreational activities (e.g. music).
Using either approach, a grid of receivers must be defined in order to measure or calculate noise levels. When results are obtained, using GIS tools, spatial interpolation must be applied in order to give a continuous graphical representation of sound levels. According to the END five dBA ranges are used for this contour (isoline) representation.