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

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

*Sound Levels*usually vary over time.

**Leq**is the equivalent continuous sound level in decibels, equal to the total sound energy measured over a stated period of time.

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

*LAeq* is the A-weighted, equivalent continuous sound level in decibels usually measured over a stated period of time, denoted LAeq,T where T is the measurement time.

**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 noise 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 class 1, 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** 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.

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

### Short Leq

**Short Leq**is the preferred modern method of storing

*sound levels*and displaying the true time history of noise events and all other sound levels during any specified period of time. The resulting 'time histories', typically measured in 1/8 second intervals may then be used to calculate the 'overall' levels for any sub-period of the overall measurement time.

See also integrating sound level meters

Leq (equivalent continuous sound level) - a more detailed explanation

SEL (sound exposure level) - the Leq normalized to 1 second, equivalent to the total sound energy.

**Related Terms**

CNEL - community noise equivalent level

Lday - day, equivalent sound level

Lden - day-evening-night, equivalent sound level)

Ldn - day-night equivalent sound level

LEP,d - daily personal noise exposure level

LEP,w - weekly personal noise exposure level

LEX,8h - daily noise exposure level

Noise Dose

Sound Energy

Sound Level and Integrating Sound Level Meters

Sound Exposure

Sound Pressure

See also the IEC Definition of Level