Sound Exposure : Definitions, Terms, Units an Measurements, see also Noise Dose
Sound Exposure IEC Definition is the time integral of squared Instantaneous A-frequency-weighted, Sound Pressure, over a stated period of time or event. The frequency weighting may be other than A, if so specified.
♦ Note 1 : Duration of integration is implicitly included in the integral, and need not be reported explicitly.
♦ Note 2: The unit of sound exposure is the pascal-squared-second (Pa2
·s), if time is in seconds and the pascal-squared-hour (Pa2
·h), if time is in hours.
(sound exposure meters) measure Pa²·h.
For a given period of time, an increase of 10 dB(A) in Sound Pressure Level corresponds to a tenfold increase in the Sound Exposure.
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% Dose
2 Pa² = 88.0 LAeq,8 h
5 Pa² = 91.9 LAeq,8 h
10 Pa² = 94.8 LAeq,8 h
Exposure Action Value : EAV
Exposure Limit Value : ELV
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 defined as the as the constant sound level that has the same amount of energy in one second as the original noise event.
Sound Exposure Level : A-weighted sound exposure levels are denoted by the symbol LAE.
Sound Exposure Level : SEL is similar to
Leq - equivalent continuous sound level as the total
sound energy is integrated over the measurement period. However instead of averaging over the measurement period, a reference duration of 1 second is used.
It follows that the sound exposure level = Leq + 10·Log10T where T is in seconds for the whole measurement period.
♦ Note : Log10 is also written as lg = logarithm to the base 10; recommended by ISO the International Standards Organisation.
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 and sources.
see also : Single Event Noise Exposure Level : SENEL
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 LEP,d - Daily Personal Noise Exposure.
See also :
Leq - Equivalent Continuous Sound Level
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