Acoustic Glossary


 

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.
 
Noise Dosimeters (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
 
see also : Exposure Action Value : EAV and 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 : : Noise Dose  l  Leq - Equivalent Continuous Sound Level.
 

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