Dorrough 40-A Specifications download pdf (Page 37)

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 PAM PiCo 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.

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Dorrough 40-A Specifications Page 37