## Leq, LAeq, LAeq,T : Equivalent Continuous Sound Levels .....

### Leq

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

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

Most community and industrial noise measurements are frequency weighted so the *LAeq* and *LAeq,T* descriptors are 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 (Fast, Slow etc.) circuits which helped the operator average the meter fluctuations by eye, but introduced other accuracy limitations.

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. The individual meter accuracy is classified in accordance with National and International Standards.

**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.

### Equivalent Continuous Sound Level - formal name for the Leq

#### Leq 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 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 (IEC 801-22-16)* should not to be confused with the equivalent continuous sound pressure level (IEC 801-22-11).

See also our sound level calculations page.

### 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

SEL : sound exposure level, the Leq normalised to 1 second, equivalent to the total sound energy.

### Leq 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