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Sound Exposure : Definitions, Terms, Units an Measurements,
see also Noise Dose
Sound Exposure is the A-weighted, Sound Pressure, squared and integrated over a stated period of time or event. The SI unit is Pa² s however the practical unit used in
Noise Dosimeters (sound exposure meters) is Pa² h. For a given period of time, an increase of 10 dB(A) in
Sound Pressure Level corresponds to a tenfold increase in E A.
1 Pa² h = 100 Dose% = 85 LAeq(8 h) = 85 dBA for 8 hours.
0.1 Pa² = 74.9 LAeq,8 h
0.2 Pa² = 78.0 LAeq,8 h
0.5 Pa² = 81.9 LAeq,8 h
1 Pa² = 84.9 LAeq,8 h = 100%
2 Pa² = 88.0 LAeq,8 h
5 Pa² = 91.9 LAeq,8 h
10 Pa² = 94.8 LAeq,8 h
Most modern sound level meters measure sound exposure and then calculate the required parameters. To see a range of Noise at Work Meters click here.
Sound Exposure Level : SEL is the Logarithmic measure of the A-weighted , Sound Pressure Level squared and integrated over a stated period of time or event, relative to a reference sound pressure value. The units are the decibel (dBA).
In practice the SEL normalized to a 1 second period was found to be extremely useful when comparing noise levels and is now commonly used and also referred to as the Sound Exposure Level, which can be confusing if not clearly stated. So
Sound Exposure Level : SEL is also any Leq noise level or event 'commonly' normalized to 1 second.
Sound Exposure Level is numerically equivalent to the total Sound Energy. For example a noise level of 90 dBA lasting 1 second would have a SEL of 90 dBA but if the event lasted 2 seconds the SEL would be 93 dBA.
Put another way if a second event of 80 dBA occurred it would have to last 10 seconds to register a 90 dBA SEL.
Sound Exposure Level, Leq and Dose are mathematically related if the Time is known.
Sound Exposure Levels, normalized to 1 second are a very useful way of comparing different sound events.
Sound Exposure Meter : a small instrument designed to be worn by an individual to provide a measure of the accumulated sound exposure received by the wearer while moving about during the workday. The instrument is calibrated in Pa².h. If the meter is worn for only a representative part of the working day, the reading must be corrected appropriately.
Also known as PSEM - Personal Sound Exposure Meter.
Noise dosemeter (or dosimeter) is a more general term for instruments having a similar purpose but may be calibrated to suit differing standards around the world.
Sound Exposure Time : the time a person is exposed to noise during a workday - used for calculation of L EP,d - Daily Personal Noise Exposure.
See also :
Leq - Equivalent Continuous Sound Level