OPTIMOD SURROUND PROCESSOR OPERATION
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CBS Loudness Meter Histogram
Maximum Meter Indication in Each 10-Second Period
Figure 3-4: Histogram sorting CBS loudness measurement
s into 1 dB bins
Histograms
The measurements can also be presented as histograms (Figure 3-4 above and Figure
3-5 on page 3-82) that sort the magnitude of the measurements into 1 dB or 1 LKFS-
wide
slices and show the number of measurements that fit into each of these slices.
The histogram thus provides an effective portrayal of the consistency of the loud-
ness — when the data are tightly clustered within a few bins, this indicates that the
loudness is more consistent than it would be if the data were spread out into a lar-
ger number of bins.
Both histograms show the loudness is well controlled, although the details are dif-
ferent. Both the BS.1770 and CBS measurements indicate that most of the data
points are in a ±1 dB window. However, the BS.1770 has low probability outliers that
are absent in the CBS graph. These outliers represent the aforementioned periods of
unadorned dialog that measure low because the BS.1770 standard does not yet
specify silence gating.
Studies indicating that BS.1770 is inaccurate at very low frequencies
In addition to its lack of silence gating, another weakness of BS.1770 is that, unlike
the CBS loudness controller and meter as implemented in Orban products, the
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