## Leq, LAeq, Equivalent Continuous Sound Level ...

### Leq., LAeq. and LAeq,T

**Leq** (equivalent continuous sound level) is the sound level in decibels, having the same total sound energy as the fluctuating level measured.

*Leq* is also known as the time-average sound level (LAT).

*LAeq* is the A-weighted *Leq sound level*.

*LAeq,T* is the A-weighted *Leq sound level*, measured over a specified period of time (T)

Most community and industrial noise measurements are A-weighted so the *LAeq* descriptor is widely used.

Early sound level meters had a very limited dynamic range, so if the sound levels fluctuated by more then 20 dB during a measurement, the accuracy was in doubt. They also used exponential averaging circuits (*Fast, Slow* etc.) which helped the operator average the meter fluctuations by eye, but introduced another accuracy limitation.

Modern integrating sound level meters monitor a wide range of fluctuating levels faithfully and the digital linear averaging circuits record and display the *Leq* (average energy) time histories and the L10, L90, Ln etc., statistical noise levels, over minutes, hours or days as required.

*Leq* is widely used, but not widely understood - click here for a more detailed explanation.

*Leq* is normally based on an exchange rate of 3 dB. An 8-hour Leq is also known as LEP,d = LEX,8h.

*Leq is the 'common' name for the equivalent continuous sound level,* see the IEC definition below

### Equivalent Continuous Sound Level

*Equivalent Continuous Sound Level*is the average sound level which over a given period of time has the same total energy as the fluctuating noise.

**Equivalent Continuous Sound Level** (IEC 801-22-16) logarithm of the ratio of a given time-mean-square, standard frequency-weighted, sound pressure for a stated time period, to the square of the reference sound pressure of 20 μPa. *Equivalent continuous sound level* in decibels is ten times the logarithm to the base ten of that ratio. Also known as the *time-average sound level*

Note 1 : if a frequency-weighting is not specified, the A-frequency weighting is understood.

Note 2 : in principle, exponential time weighting is not involved.

Equivalent continuous sound level should not to be confused with the equivalent continuous sound pressure level.

See also our sound level calculations article