## Leq, LAeq, Equivalent Continuous Sound Level, Definitions, Terms, Units, Measurements etc., ..

**Leq**is the equivalent sound level in decibels, equivalent to the

**total**sound energy measured over a stated period of time and is also known as the

*equivalent continuous sound level*and the

*time-average sound level (LAT)*.

**LAeq** is the equivalent sound level in decibels equivalent to the **total** A-weighted sound energy measured over a stated period of time. **Most community and industrial noise measurements are A-weighted so the LAeq descriptor is 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 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 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. 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 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. *Time-average 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.

The *equivalent continuous sound level* should not to be confused with the *equivalent continuous sound pressure level*. To compare these definitions directly click here

**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 - the more detailed explanation

*SEL* ▷ Sound Exposure Level = Leq normalised to 1 second, equivalent to the total sound energy.

Related Terms •

*CNEL* ▷ Community Noise Equivalent Level

*LAIeq* ▷ A-weighted, Impulse, Leq.

*LCeq* ▷ C-weighted, Leq.

*Lday* ▷ Day equivalent level

*Lden* ▷ Day-evening-night equivalent level

*Ldn* ▷ Day-night equivalent level

*LEX,8h* ▷ Daily Exposure Level

*LEP,d* ▷ Daily Personal Noise Exposure

*LEP,w* ▷ Weekly Personal Noise Exposure

Noise Dose

Sound Energy

Sound Level and Integrating Sound Level Meters

Sound Exposure

Sound Pressure

See also • the IEC Definition of Level