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OPTIMOD-PC
DWNEXP THR ("Downward Expander Threshold") determines the level below which
the single-ended noise reduction system's downward expander begins to decrease
system gain, and below which the high frequencies begin to become low-pass fil-
tered to reduce perceived noise. Activate the single-ended dynamic noise reduction
by setting the D
WNEXP
The single-ended noise reduction system combines a broadband downward ex-
pander with a program-dependent low-pass filter. These functions are achieved by
introducing extra gain reduction in the five-band compressor. You can see the effect
of this extra gain reduction on the gain reduction meters.
Ordinarily, the gating on the AGC and five-band compressor will prevent objection-
able build-up of noise, and you will want to use the single-ended noise reduction
only on unusually noisy program material. In sound for picture, it is particularly use-
ful in live news and sports.
Please note that it is impossible to design such a system to handle all program mate-
rial without audible side effects. You will get best results if you set the D
control of the noise reduction system to complement the program material you are
processing. The D
when the input is relatively quiet. The best way to adjust the D
to start with the control set very high. Reduce the control setting while watching
the gain reduction meters. Eventually, you will see the gain increase in sync with the
program. Go further until you begin to hear noise modulation—a puffing or breath-
ing sound (the input noise) in sync with the input program material. Set the D
T
control higher until you can no longer hear the noise modulation. This is the
HR
best setting.
Obviously, the correct setting will be different for a sporting event than for classical
music. It may be wise to define several presets with different settings of the D
control, and to recall the preset that complements the program material of the
T
HR
moment.
Note also that it is virtually impossible to achieve undetectable dynamic noise reduc-
tion of program material that is extremely noisy to begin with, because the program
never masks the noise. It is probably wiser to defeat the dynamic noise reduction
with this sort of material (traffic reports from helicopters and the like) to avoid ob-
jectionable side effects. You must let your ears guide you.
B3>B4 CPL ("Band 3>4 Coupling") control determines the extent to which the gain
of band 4 (centered at 3.7 kHz) and 5 (above 6.2 kHz) are determined by and follows
the gain of band 3 (centered at 1 kHz). Set towards 100% (fully coupled) this control
reduces the amount of dynamic upper midrange boost, preventing unnatural upper
midrange boost. The gain of band 5 is further affected by the B4>B5 CPL control.
Excessive HF energy is one cause of audibly objectionable artifacts in low bitrate co-
decs. The B3>B4 C
facts—setting them for large amounts of coupling will minimize OPTIMOD-PC's abil-
ity to dynamically increase high frequency energy.
T
control to a setting other than OFF.
HR
E
T
should be set higher when the input is noisy and lower
WN
XP
HR
B4>B5 C
controls can be very useful in reducing such arti-
PL AND
PL
OPERATION
E
T
WN
XP
HR
E
T
control is
WN
XP
HR
E
WN
XP
E
WN
XP
3-49
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