Acoustic Glossary

Sound Exposure: Definitions, Terms, Units and Parameters - 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 EA.

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 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 so this is now commonly used and also referred to as the Sound Exposure Level.

Sound Exposure Level : SEL : is any Leq noise level or event 'commonly' normalized to 1 second.

SEL = Leq + 10·Log10T  where T in seconds. Log10 is also written as lg = logarithm to the base 10

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.

see also : Single Event Noise Exposure Level

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.