Linear Acoustic LQ-1000 User Guide
Applications and Use
15
Figure 3-2
Responses of the pre-filter to account for acoustic effects of the head (left), and the RLB
high-pass filter (right) combine to produce the so-called K-weighting filter.
The final output of this system is Loudness, K-weighted, with respect to Full Scale, or
dBLKFS. If a 1kHz tone is applied to the L, C, or R inputs of this system, the output will
indicate approximately -3 dBLKFS, and if applied to Ls or Rs will indicate approximately
-1.5 dBLKFS.
The intention of the standard is to measure the loudness of a program over the entire
length of the program. While this works nicely for pre-recorded content, it does not make
for a useful tool for real-time use. One important part of this measurement that is not yet
part of the standard is integration time. The current metering system will produce instan-
taneous results, but these are relatively useless because the resulting measurement varies
too much and “eyeball interpretation” is once again required.
Longer integration times settle the measurement down and produce a value that correlates
better with what a user actually hears and is steady enough to be useful. Scholarly research
by Gilbert Soulodre of the Canadian Research Centre (CRC) and Jeffrey Riedmiller of Dol-
by Laboratories have suggested that a minimum useful integration time is 3 seconds and
that for practical metering a 10 second average is useful. The recent work of the European
Broadcasting Union (EBU) is suggesting that including an even faster value could be help-
ful.
3.1.2
EBU Recommendation R128
The LQ 1000 supports the new EBU R128 recommended practice for loudness metering.
This new mode adds Relative Gating, display of Momentary, Slow, and Integrated loud-
ness, and Loudness Range indication. These measurements are also captured in a Session
log and an always-running 7.5-day Weekly log, all of which can be exported via USB. EBU
mode runs simultaneously with standard ITU mode and all measurements are always avail-
able.
Summary of Contents for LQ-1000
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