User`s manual

LM6 - Radar Loudness Meter / 19
EN
Level versus Loudness
Whenlevelnormalizationinaudiodistributionisbasedonapeaklevelmeasure,it
favors low dynamic range signatures as shown in Fig 1. This is what has happened
to CD.
Quasi-peak level meters have this effect. They tell little about loudness, and also
requireaheadroominordertostayclearofdistortion.UsingIEC268-18meters,the
headroom needed is typically 8-9 dB.
Sample based meters are also widely used, but tell even less about loudness. Max
sample detection is the general rule in digital mixers and DAWs. The side effect of
using such a simplistic measure has become clear over the last decade, and CD
music production stands as a monument over its deficiency. In numerous TC papers,
it has been demonstrated how sample based peak meters require a headroom of at
least 3 dB in order to prevent distortion and listener fatigue.
The only type of standard level instrument that does not display some sort of
peak level is the VU meter. Though developed for another era, this kind of meter
is arguably better at presenting an audio segment’s center of gravity. However, a
VUmeterisnotperceptuallyoptimized,oridealforlookingataudiowithmarkedly
different dynamic range signatures.
Unlikeelectricallevel,loudnessissubjective,andlistenersweighitsmostimportant
factors - SPL, Frequency contents and Duration - differently. In search of an
“objective”loudnessmeasure,acertainBetweenListenerVariability(BLV)and
WithinListenerVariability(WLV)mustbeaccepted,meaningthatevenloudness
assessments by the same person are only consistent to some extent, and depends
on the time of day, her mood etc. BLV adds further to the blur, when sex, culture, age
etc. are introduced as variables.
Because of the variations, a generic loudness measure is only meaningful when it is
basedonlargesubjectivereferencetestsandsolidstatistics.TogetherwithMcGill
University in Montreal, TC Electronic has undertaken extensive loudness model
investigation and evaluation.
The results denounce a couple of Leq measures, namely A and M weighted, as
genericloudnessmeasures.Infact,aquasi-peakmetershowedbetterjudgement
ofloudnessthanLeq(A)orLeq(M).Evenusedjustforspeech,Leq(A)isapoor
pick, and it performs worse on music and effects. An appropriate choice for a low
complexity, generic measurement algorithm, which works for listening levels used
domestically,hasbeenknownasLeq(RLB).
Combined loudness and peak level meters exist already, for instance the ones
fromDorroughs,butBS.1770nowoffersastandardizedwayofmeasuringthese
parameters.
In2006,ITU-RWorkingParty6Jdraftedanewloudnessandpeaklevelmeasure,
BS.1770,andthestandardhassubsequentlycomeintoeffect.Ithasbeendebated
if the loudness part is robust enough, because it will obviously get exploited where
possible.However,withavarietyofprogrammaterial,Leq(RLB)hasbeenverified