Orban OPTIMOD 6300 Operating Manual page 47

OPTIMOD 6300 DIGITAL
 The "neutral" setting of the D
the loudness of 6300 version 1.x processing) is –19 dB.
 Because loudness perception combines the contributions of all acoustic
sources, there is only one Loudness Level meter indication regardless of the
number of audio channels.
The BS.1770-2 meter is well described by its governing standards docu-
ment. Based on our listening tests and feedback from mixing engineers
involved with major network productions, we believe that the short-term
(3-second integration time) meter can over-indicate the loudness of the
"anchor element" (usually speech) by as much as 5 dB in two important
cases. The first is where the material has a low peak-to-RMS ratio because
a large amount of "artistic compression" has been applied with the goal
of adding color and excitement to promos and commercials. The second
is where is the dialog passages contain substantial amounts of underscor-
ing and/or effects, particularly if these have a large amount of energy be-
tween 100 and 300 Hz. These issues have caused frustration for producers
and mixers who have had to compromise their mixes to prevent them
from airing too quietly in broadcast processing chains that rely on auto-
mated use of the BS.1770 meter to set final on-air loudness.
To satisfy customers who rely on BS.1770-centric automated loudness
quality control procedures, the 6300 has a "BS.1770 safety limiter" that
prevents the long-term BS.1770-2 loudness from exceeding a user-
adjustable threshold. It is set for a ten-second integration time. However,
because the 6300's CBS Loudness Controller is better able to lock onto
the "anchor element" than is the BS.1770 meter, we believe that the
processed audio sound more naturally pleasing and consistent if the
BS.1770 safety limiter is defeated. We offer one factory preset where this
limiter is defeated: TV 5B GP NO1770 LC.
The CBS meter is a "short-term" loudness level meter that displays the
details of moment-to-moment loudness with dynamics slightly faster
than a VU meter. It can indicate the loudness of short-term sounds (like
pistol shots) that may be annoying to TV viewers but that the BS.1770-2
meter, because of its longer integration time, may not take fully into ac-
count. Created using Orban-developed modeling software, the DSP im-
plementation typically matches the original CBS analog meter within 0.5
dB on sinewaves, tone bursts and noise.
The Jones & Torick algorithm improves upon the original loudness meas-
urement algorithm developed by CBS researchers in 1967. Its foundation
is psychoacoustic studies done at CBS Laboratories over a two year period
by Torick and the late Benjamin Bauer, who built on S. S. Stevens' '50s-
era work at Harvard University.
After surveying existing equal-loudness contour curves (like the famous
Fletcher-Munson set) and finding them inapplicable to measuring the
loudness of broadcasts, Bauer and Torick organized listening tests that
resulted in a new set of equal-loudness curves based on octave-wide
noise reproduced by calibrated loudspeakers in a semireverberant 16 x 14
x 8 room, which is representative of a room in which broadcasts are nor-
IALNORM control (i.e., the setting that matches
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INTRODUCTION