16
Step 3. Use the slider to adjust the
Phase
(one slider)
–
128 (default); When monitoring a stereo signal, the coherence between the 2 channels (i.e.,
how similar they are) greatly affects its mono compatibility. The phase meter indicate the
relative phase of the 2 channels and thereby provide some measure of mono compatibility.
Phase meter reading in the upper half of the scale indicate acceptable mono compatibility,
whereas lower half readings warn of a potential compatibility problem.
Use the slider to adjust the
VU
(volume unit
– one slider) – refer to the above figure
Alignment
:
–27.9 dBFS (decibels relative to full scale; default);
user adjustable; also known as safe range.
Alarm
: 0 to
–13.95 dBFS (default);
0 to
–20 dBFS depending on “alignment” setting; the “alarm” range is equivalent to the upper
half of 0 dBFS minus previous item
“alignment” setting.
Headroom
:
–14 to –27.9 dBFS (default);
–20.7 to –41.58 dBFS depending on “alignment” setting the “headroom” range is equivalent to
the lower half of 0 dBFS minus
“alignment” setting; also known as the headroom before alarm
range is reached.
Use the slider to adjust the
Sound
(
H
igh/
L
ow sliders).
For 3G / HD-SDI signal
– selecting the primary channel without embedded audio will cause the secondary
channel to lose its audio output.
Step 5. Use the slider to adjust the
Width
and the
Transparency
of the meter appearing on screen.
Step 6.
Select the meter’s
Ballistics
(absolute movement of the meter's pointer). Meters which monitor
audio levels are typically one of two varieties: VU (Volume Unit) or PPM (Peak Program
Meters). Though both perform the same function, they accomplish the function in very different
manners. A VU meter displays the average volume level of an audio signal (relatively slower
response and is driven from a full-wave averaging circuit). A PPM displays the peak volume
level of an audio signal (shorter integration time so that only peaks wide enough to be audible
are displayed).
For a steady state sine wave tone, the difference between the average level (VU) and the peak
level (PPM) is about 3 dB. But for a complex audio signal (speech or music), the difference
between the average level (VU) and the peak level (PPM) can be 10 to 12 dB. This difference
between the reading of a VU meter and a PPM is known as the crest factor.
Whereas the VU meter has fairly equal attack and release times, the PPM is characterized by
having a very slow fall-back time, taking over 1.5 seconds to fall back 20dB. The reasoning for
the slow fall-back was to reduce eye-fatigue and make the peak indication easier to assimilate.
