Studio Technologies 76DBA V.3.00 - Manual (Page 43)

Model 76DBA/77B User Guide Issue 1, November 2010
Studio Technologies, Inc. Page 43
for Surround
are intended to represent the sound pres-
sure level in dB SPL, a figure that should
directly relate to the actual sound pressure
level that the surround loudspeaker system
is presenting to users. (Typically, the level
value would actually be in dBC, the C-
weighted sound pressure level.) When the
reference level button is enabled, or the
rotary level control is set so that the refer-
ence level has been reached, the display
will typically show something in the range
of 82 to 87 dB. Assuming that the monitor-
ing environment has been correctly cali-
brated, this would indicate that an average
listening level of 85 dB, for example, had
been achieved.
Dialnorm Display
When the 4-digit display is set for the
dialnorm display mode a much different
piece of information will be shown to the
user. It will show the somewhat obscure
but important dialnorm level parameter
that’s associated with a surround input
source. As has been covered in other parts
of this user guide, dialnorm is intended to
provide a numeric value that represents
the average dialog level associated with
an audio-for-picture element. Technically,
dialnorm values can range from –31 to
–1 dB but during actual operation they
will typically be in the range of –30 to
–20 dB. The value may change relatively
frequently in conjunction with changes to
the actual audio signal level. This would
be the case, for example, with a televi-
sion program that consists of alternat-
ing program and advertising segments.
In other situations the dialnorm level will
only change when an “on-air” source is
switched from typical station-originated
segments to an extended-duration broad-
cast network program, such as a live
concert event. It’s also possible that in some
facilities the dialnorm level is fixed and won’t
ever change. That’s not really in the spirit
of what dialnorm is supposed to accom-
plish, but c’est la vie. Whatever the dialnorm
level—the Model 77B will display it!
In both display modes a special feature is
provided to assist users in knowing if the
current dialnorm level matches a facility’s
“house” reference. This reference level,
typically in the range of –24 to –27 dB, is
entered as part of the Model 77B’s configu-
ration process. The “dot” in the lower-right
corner of the 4-digit display will light when-
ever the current dialnorm level matches
the stored reference level. Refer to Figure
10. This feature can be useful in broadcast
transmission and distribution applications.
In theory, any time the dot in the lower-right
corner is not lit the current dialnorm level
value is causing a level adjustment to take
place. This level adjustment may be tak-
ing place on the post-fader surround digital
and analog monitor outputs if the dialnorm
enable function is active, as it would be for
downstream users of the broadcast signal.
Note that if a valid dialnorm source is not
available the 4-digit display, when selected
to display dialnorm, will show four dashes
Figure 10. Incoming Dialnorm Level Match “Dot”