Studies Indicating That Bs.1770 Is Inaccurate At Very Low Frequencies - Orban OPTIMOD 6300 Operating Manual

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OPERATION ORBAN MODEL 6300
Some studies have indicated that when people are asked to assess the loudness of a
given piece of material, they state that it sounds louder when underscoring or ef-
fects are added to constant-level dialog. The EBU has used these studies to justify
the position taken in R 128 that a listener's impression of total loudness is more im-
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portant than dialog level . In our opinion, this misses the point. A more relevant
question is whether viewers would want to turn down their volume controls to
make dialog quieter when underscoring and effects appear. (In other words,
whether effective TV commercial loudness control requires nothing more than ap-
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plying gain control to commercials such that the BS.1770-2 "short-term" loudness
is always limited to 0 LK.) Regarding this, Orban and Dolby Labs hold similar views.
We believe that dialog is the most important element in most television audio and
that listeners do not want to turn down their volume controls every time that un-
derscoring or effects appear under the dialog. The popular Dolby LM100 Loudness
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Meter in its current revision uses the same Leq(RLB) algorithm as BS.1770 but adds
gating to eliminate non-speech material, including silence. The author has used the
Dolby LM100 to measure the output of the Orban 8685 with a wide variety of
speech material, and has observed that this material is almost always controlled
within a ±1 dB window as measured on the LM100. In the author's opinion, this
demonstrates the benefits of a dialog-centric measurement. Moreover, the author
believes it is unwise to rely on a BS.1770 measurement to set the on-air loudness of
unadorned dialog because this can cause the dialog to be too loud with respect to
other material. The author has experimented with "inverse short-term BS.1770
loudness control" and believes that it sounds unnatural, pumping dialog loudness
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up and down in a subtly inartistic way as underscoring and effects come and go.

Studies indicating that BS.1770 is inaccurate at very low frequencies

Another weakness of BS.1770 is that, unlike the CBS loudness controller and meter
as implemented in Orban products, the BS.1770 algorithm does not take into ac-
count the loudness contributed by the LFE channel, for good reason. Nacross and
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Dash, Ian; Bassett, Mark; Cabrera, Densil, "Relative Importance of Speech and
Non-Speech Components in Program Loudness Assessment," AES Convention Paper
8043, 128th AES Convention (May 2010).
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EBU R 128 specifies short-term loudness as a BS-1770-1 (ungated) measurement
with a three-second integration time.
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http://www.dolby.com/professional/products/broadcast/test-and-
measurement/lm100.html
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See Begnert, Fabian; Ekman, Håkan; Berg, Jan, "Difference between the EBU R-
128 Meter Recommendation and Human Subjective Loudness Perception," AES Con-
st
vention Paper 8489, 131 AES Convention, (October 2011). This paper states, "These
loudness-equalized signals gave rise to a perceived maximum loudness difference of
2.8 dB." This is very close to the 3 dB number that has come up in other discussions
(such as the one quoted in footnote 10 on page 3-85). While the authors of this pa-
per consider 3 dB to be insignificant, others do not necessarily share this view, par-
ticularly advertisers who hear their expensive commercials aired 3 dB quieter than
surrounding program material!