## 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 Definition

Equivalent Continuous Sound Level Definition(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 levelin decibels is ten times the logarithm to the base ten of that ratio. Also known as thetime-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 equivalent continuous sound pressure level.

See also our sound level calculations article