Dante Inovonics 541, Installation & User Manual, Page: 28 / 56

— 24 —
reasonable stereo activity.
Left
and
Right
meters do not factor-in
phase differences between the stereo channels, and phase dif-
ferences can play a big part in stereophonic pereception.
XTalk (stereo crosstalk) is similar to the Sep (stereo separation)
measurement, but in this case it indicates the level difference
between the L+R and L-R program audio components. Like the
Sep
readout, it is useful only with tone tests and is not an indi-
cation of crosstalk issues in the program audio.
FM Program
Loudness
The measurement of FM program loudness adheres to a Stand-
ard of European origin that has become a de-facto means of as-
sessing this parameter worldwide, both in radio and in televi-
sion broadcasting.
The ITU-R
BS.1770
Loudness
Standard
The ITU-R BS.1770 Standard is ostensibly based on listener
perception of audio loudness. Meter readings under this
standard are expressed in “LUs” (Loudness Units), one LU in-
crement equivalent to 1dB. In using this function, it’s best to
consider LU measurements as “locally-relative,” or most useful
in comparing loudness between various audio sources, market
companions, music cuts, processing presets, talent voices, etc.
‘Zero-LU’ does not conveniently correlate to a specific modula-
tion percentage because of the Standard’s specified frequency
weighting. However, a 1kHz constant tone at the nominal 100%
modulation (±75kHz deviation) point would drive the meter to
about +22LU.
Loudness metering has a 100ms refresh rate. ‘LU’ is displayed
as a bargraph featuring three color-coded
Loudness (LU)
indica-
tor bar-segments labeled Momentary , Short-Term and Integrated , or
‘M,’ ‘S,’ and ‘I.’
The yellow segment shows a ‘momentary’ value of loudness, ac-
tually the loudness of a floating 400ms block of audio updated
at the 100ms refresh rate. This gives the best ‘right now’
measurement of loudness. The yellow ‘wash’ behind the dis-
play represents the range of gated ‘M’ within the ‘I’ measure-
ment window, providing a visual representation of program dy-
namic range.
The green segment represents a short-term-integrated value de-
rived from a 3-second block of audio refreshed every second, a
readout primarily indicating the loudest sections of program
audio.
The blue segment is a longer-term integrated measurement that
is ‘gated’ to ignore speech pauses and other periods of silence.
This is probably the most useful overall, average-program-
loudness reading.