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Sound Exposure Level (L
AE
)
Like sound exposure it is a measure of the total A-weighted sound energy of the
sound produced over a specified period of time, however it is expressed in dB.
The sound exposure level is used to describe the amount of noise from a single
event such as an aircraft flying overhead or a train pass by.
It is the integration of all the acoustic energy contained within this single event
over the time period t2-t1 with reference to a sound pressure of 20µPa
consistent over a reference time period of 1 second.
See ‘Function Equations’ to see how LAE is described mathematically.
Sound Power (W)
This is the rate of flow of acoustic energy emitted from a specific sound source.
Sound power is expressed in watts (W).
Sound Power Level (L
W
)
Like sound power this is the rate of flow of acoustic energy emitted from a
specific sound source, however the sound power level is expressed in decibels
(dB).
L
w
10 log
W
W
o
⋅
dB
:=
where Wo is the reference power of 1 Pico watt (10
-12
watts) and W is the
sound power.
It is often quoted on machinery to indicate the total sound energy radiated per
second.
Sound Pressure
This is the difference between the ambient sound pressure and the
instantaneous sound pressure caused by a noise source.
The sound pressure is expressed in Pascal’s (Pa).
