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Loudness & Terminology
About Loudness
Loudness measurements differ from conventional signal amplitude measurements in that they are also influenced
by the frequency content of the signal and the duration of transient components. The way these various
elements are handled to give a value for display has been defined by the International Telecommunications
Union in their standard ITU BS1770 which is the only loudness standard to have achieve any degree of
international acceptance.
The DK Meter allows a number of parameters to be adjusted to suit whatever options your organisation and
perhaps regulatory body has decided to mandate.
Two organisations leading the way in the standardisation of loudness measurements are the Advanced Television
Systems Committee (ATSC) in the USA and the European Broadcasting Union (EBU) in Europe. The background
information to the measurement norms is contained in the ATSC document "Techniques for establishing and
maintaining audio loudness for digital television", document A/85:2011. The EBU document R128 is
supplemented by EBU Tech 3341, 3342, 3343 and 3344 between them they define a number of terms and set
out the reasons behind many of the objectives of loudness measurements.
Terminology
The Loudness world includes a number of terms and abbreviations worth noting:
Loudness Range (LRA)
Loudness range is a statistic calculation of the material's dynamic range based on the short term (sliding)
loudness (3 secs). Loudness Range is abbreviated 'LRA'.
Momentary Loudness (M)
Momentary loudness is the sum of the RLB weighted audio channels and integrated over 400ms. Momentary
loudness is used to calculate short term and integrated loudness Momentary Loudness is abbreviated 'M'.
Short Term Loudness (S)
Short term loudness is a 3 seconds integration of the momentary loudness. (10 and 30 seconds are also used in
some standards/regions). Short Term Loudness is abbreviated 'S'
Absolute Gated Integrated Loudness
The absolute integrated loudness is a long term measurement (an integration over the entire material) based on
the momentary loudness. It uses an absolute gate at -70LUFS/LKFS (M) which means that if the momentary
loudness is getting under -70LUFS/LKFS then the measurement holds until the momentary loudness goes above.
The absolute loudness is not used directly by the user, but is used to calculate the dynamic gate. The dynamic
gate is, according to ITU-R BS.1770-2, -10 LU below the absolute gated loudness.
Dynamic Gated Integrated Loudness (I)
The dynamic gated loudness is a long term measurement (an integration over the entire material) based on the
momentary loudness.
It uses a dynamic gate at -10 LU under (dB relative to) the absolute gated loudness which means that the
measurement is on hold if the momentary loudness gets under the dynamic gate.
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