Acoustic Glossary


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


is the sound level in dB, equivalent to the total sound energy over a stated period of time, see the IEC Definition below.


Leq is normally based on an exchange rate = 3. and the 8 hour Leq level is also known as LEP,d = LEX,8h.

Leq is widely used, but not widely understood - click here for a more detailed explanation.
Leq is also referred to as the Equivalent Sound Level and the Time-average Sound Level
To see a range of Leq Meters click here.

Leq IEC Definition, 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. The Leq 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.

Leq : Equivalent Continuous Sound Level is also known as the Time-average Sound Level


it is good practice to include other measurement parameters, such as A-weighting, so other people are aware of how the measurement was made; other examples include:-

LAeq,t : A-weighted equivalent sound pressure level in dB measured over a period of time t.

LCeq,t : C-weighted equivalent sound pressure level in dB measured over a period of time t.

Short Leq

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.

Related Terms :
CNEL : Community Noise Equivalent Level
LAIeq : A-weighted, Impulse, Leq, Sound Pressure Level.
LAT : Time Averaged Sound Level
LCeq : C-weighted, Leq, Sound Pressure Level
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