TC Electronic Broadcast 6000 - Manual (Page 193)

Backdrop
English Manual 189
put signal is relatively high, you will likely begin to
hear strange low-level random chirping sounds.
These low-level artifacts are usually referred
to as “musical noise” or sometimes as “Mars-
men”, or “space monkeys”. These artifacts are
commonly found in other noise reduction prod-
ucts and can seriously limit the usability of the
noise reduction system. Fortunately, BackDrop
provides you with a means of eliminating these
artifacts.
Slowly increase the level of the Basilar Disper-
sion parameter. You should hear the musical
noise artifacts disappear. This is exactly the pur-
pose of the Basilar Dispersion parameter. By
taking advantage of the masking properties of
the ear, Basilar Dispersion eliminates low level
artifacts that can occur as a result of the noise
reduction process.
To further investigate BackDrop’s controls, set
Aggression and Basilar Dispersion to 100 % and
set Max Reduction to 100 dB. You are now ap-
plying the maximum amount of noise reduction
available from BackDrop. With this amount of
noise reduction you will very likely hear distor-
tions to the desired signal.
For example, you may hear a smearing of the
transient portions of the signal. BackDrop’s
Transient Recovery parameter was specifically
designed to maintain sharp attacks and to pre-
vent transients from being smeared. Increase the
Transient Recovery control and listen to how the
transients are restored to their original sound.
Hopefully, you now have a feel for the four pri-
mary controls for BackDrop’s Basic algorithm.
The controls for the other two algorithms (Multi-
Band and MultiType) are similar in functionality.
Remember that the settings for BackDrop’s con-
trols described in this tutorial are by no means
the recommended settings. They were simply
intended to help you become familiar with their
effect.
It is instructive to play some more with the vari-
ous controls and to listen to the amount of noise
reduction, the occurrence of musical noise, and
the smearing of transients (signal distortion).
These variables must be balanced when using
BackDrop to remove noise from your audio. For-
tunately, BackDrop provides you with a compre-
hensive set of tools to make the optimal possible
trade-off.
When using BackDrop’s controls it is important
to remember that Aggression and Max Reduc-
tion work together and so you should go back
and forth between these parameters in order to
find the best settings. This also applies to the
Basilar Dispersion and Transient Recovery con-
trols which work together.
Backdrop algorithm
– advanced Use
The tutorial in the previous section was intended
to give you a feel for some of BackDrop’s con-
trols. In this section we endeavor to provide you
with some guidelines for obtaining the best pos-
sible performance from BackDrop. The following
steps have been found to be a suitable approach
for getting good performance under almost all
circumstances. As you become more familiar
with BackDrop you will no doubt develop your
own techniques and strategies that work best
for you.
As always, the first step in the noise reduction
process is to capture a sample of the audio for
the noise print information. It is very important
that the audio used to calculate the noise print
information contain only the noise and none of
the signal.
With the noise print information calculated, use
the Algorithm Model control to select the Back-
Drop algorithm (Basic, MultiBand or MultiType)
that is best suited to the noise you are trying to
remove.
BackDrop’s fundamental philosophy is to target
the noise reduction to where it is needed most
and to apply as little processing as possible to
the signal. The strategy outlined in this section is
in keeping with this philosophy. Generally speak-
ing, to get the best results from BackDrop, do
not be “over aggressive”. Try to use as low an
amount of aggression, and Max Reduction as
possible, and use a moderate amount of Basilar
Dispersion (40 % to 60 %).
It is useful to begin by getting an idea of how
much noise reduction is necessary for the au-
dio sequence that you are working on. In many
cases reducing the noise by only a few decibels
will make a dramatic improvement in the quality
of the audio sequence. In most cases, you will
not need more than about 10 dB of noise reduc-
tion. To determine how much noise reduction is
necessary, set Basilar Dispersion and Transient
Recovery to 0 %. Set Aggression to 100 % and