Sound Exposure (E) is the time integral of the sound-pressure2 and measurements are normally A-weighted to relate directly to the human response. The SI unit of sound exposure is the pascal-squared-hour (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.
0.2 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
● 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.
Most modern sound level meters measure sound exposure and then calculate the required parameters.See also daily noise exposure • noise exposure category • noise exposure forecast
Sound Exposure Level is similar to the 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.
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 Levels normalized to 1 second are a very useful way of comparing different sound events and sources.
● Note : the reference sound pressure and the frequency weighting may be different, if specifically stated with the sound exposure level.
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.
Sound Exposure Meters measuring Pa²·h directly are also known as noise dosimeters.
Noise Dosimeter or Noise Dosemeter is a more general term for instruments having a similar purpose but may be calibrated to suit differing standards around the world.
See also • noise dose • Leq (equivalent continuous sound level)