TC Electronic Broadcast 6000 - Manual (Page 161)

LM6
English Manual 157
LM6
LM6 represents a quantum leap away from sim-
ply measuring audio level to measuring per-
ceived loudness. The old level method is respon-
sible for unacceptable level jumps in television,
for music CDs getting increasingly distorted, and
for different audio formats and program genres
becoming incompatible: Pristine music tracks
from the past don’t coexist with new recordings,
TV commercials don’t fit drama, classical music
or film and broadcast doesn’t match. The most
fundamental audio issue of all – control of loud-
ness – every day makes millions of people adjust
the volume control over and over again.
LM6 is part of a universal and ITU standard-
ized loudness control concept, whereby audio
may easily and consistently be measured and
controlled at various stages of production and
distribution. LM6 works coherently together with
other TC equipment, or with equipment of other
brands adhering to the same global standard.
Follow the guidelines given to allow audio pro-
duced for different purposes to be mixed, with-
out low dynamic range material such as com-
mercials or pop CD’s always emerging the loud-
est.
– Loudness meter fully compliant with EBU
R128
– Loudness meter fully compliant with ATSC
A/85
– Loudness meter fully compliant with ITU-R
BS.1770
– Loudness meter fully compliant with ITU-R
BS.1770-2
– Radar meter showing Momentary and Short-
term loudness
– True-peak bar-graph meters
– Advanced Logging functionality
Introduction
Since 1998, TC has performed listening tests
and evaluation of loudness models; and there-
fore holds an extensive, Universal Database of
loudness, based on ten thousands of assess-
ments. The database covers all sorts of broad-
cast material, music, commercials, feature film
and experimental sounds, and is verified against
other independent studies.
Fig 1.
Left: DRT for consumers under different listen-
ing situations
Right: Peak level normalization means that ma-
terial targeted low dynamic range platforms
gets loud.
The Universal Database is authoritative from an
academic as well as a practical point of view. It
has been indispensable when designing the LM6
meter, because it provided the missing link be-
tween short-term and long-term loudness, and
enabled the statistically founded Universal De-
scriptors of LM6 .
The chart of Dynamic Range Tolerance in Fig 1
is a side-effect of the studies mentioned: Con-
sumers were found to have a distinct Dynamic
Range Tolerance (DRT) specific to their listen-
ing environment. The DRT is defined as a Pre-
ferred Average window with a certain peak level
Headroom above it. The average sound pressure
level, which obviously is different from one listen-
ing condition to another, has to be kept within
certain boundaries in order to maintain speech
intelligibility, and to avoid music or effects from
getting annoyingly loud or soft.
Audio engineers instinctively target a certain
DRT profile when mixing, but because level nor-
malization in broadcast and music production
is based on peak level measures, low dynamic
range signatures end up the loudest as shown
by the red line in Fig 1, right. Audio production is
therefore trapped in a downwards spiral, going
for ever decreasing dynamic range. By now, the
pop music industry is “right of” In Flight Enter-
tainment in the illustration.
LM6 offers a standardized option: The visualiza-
tion of loudness history and DRT in combina-