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Percentiles (LN%)
Expressed in dB, the Percentiles represent the time-weighted sound pressure level which is
exceeded N% of a specific time interval. Typical percentiles are L1%, L5%, L10%, L50%, L90%, L95%
and L99%.
Sound Exposure Level (SEL or LE)
Expressed in dB, the SEL (or LE) represents the total energy level of a sound pressure signal observed
for a specific time interval.
T is the averaging time interval;
p(t) is the sound pressure signal;
p
0
is the reference sound pressure (2x10
-5
Pa.)
Frequency Weighting (A, C, Z)
The A, C and Z frequency weightings refer to signal filters applied to the sound pressure signal. The
figure below shows the frequency response of each filter.
Note that all sound level metrics (SPL, Leq, SEL, Lpk, Lmax, Lmin, and LN%) can be expressed with a
specific frequency weighting. For example, the LAeq represents the A-weighted Equivalent
Continuous Sound Level.
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