Manual

LM2 (optional)
Loudness Pilot English Manual (2014-10-07) 98
TC’s Universal Database of Loudness
Since 1998, TC has performed listening tests
and evaluation of loudness models. From these
tests, TC has built an extensive Universal Data-
base of loudness, based on tens of thousands
of assessments. This database covers all sorts
of broadcast material, music, commercials, fea-
ture film and experimental sounds, and is verified
against other independent studies.
The Universal Database is authoritative from an
academic as well as a practical point of view. It
has been indispensable when designing the LM2
meter, because it provided the missing link be-
tween short-term and long-term loudness, and
enabled the statistically founded Universal De-
scriptors of LM2.
Fig. 46.: Fig. 1
Left: Dynamic Range Tolerance
(DRT) for consumers in different
listening situations
Right: Peak level normalization
means that material targeted at
low dynamic ranges gets loud.
The chart of Dynamic Range Tolerance in Figure
1 is a side-effect of the studies mentioned: Con-
sumers were found to have a distinct Dynamic
Range Tolerance (DRT) specific to their listening
environment. The DRT is defined as a Preferred
Average window with a certain peak level Head-
room above it. The average sound pressure level
(which obviously is different from one listening
condition to another) has to be kept within cer-
tain boundaries in order to maintain speech intel-
ligibility, and to avoid music or effects from get-
ting annoyingly loud or soft.
Audio engineers instinctively target a certain Dy-
namic Range Tolerance profile when mixing. But
because level normalization in broadcast and
music production is based on peak level mea-
sures, low dynamic range signatures end up the
loudest as shown by the red line in Fig1.
Audio production is therefore trapped in a down-
ward spiral, going for ever decreasing dynamic
range. By now, the pop music industry is to the
right of In-flight entertainment as shown in the il-
lustration.
LM2 offers a standardized option. The visualiza-
tion of loudness history and DRT – in combina-
tion with long-term descriptors from production
onwards – is a transparent and well-sounding al-
ternative to our current peak level obsession; not
only for music, but also in production for broad-
cast or film.
An engineer – who may not be an audio expert –
should be able to identify and consciously work
with loudness developments within the limits of
a target distribution platform – and with predict-
able results when the program is transcoded to
another platform.
LM2 therefore color-codes loudness, making it
easy to identify…
►
target level (green),
►
below-the-noise-floor level (blue) and
►
loud events (yellow).
See Fig 2: