| The
Art of Noise Gates |
March
2007 |
On Stage
Go to any rock or pop concert these days and have
a good look at the sound engineer's effects rack.
Chances are you will see a few Drawmer DS201 Dual
Channel Noise Gates in the rack. These are invaluable
tools for live shows, particularly when the concert
hall has very 'live' acoustics with lots of reflections.
In these situations noise gates can be used to clean
up a live mix and really enhance the clarity of individual
instruments.
For example, let's say we've just miced and sound-checked
the drums. The kit sounds nice but there's a nasty
ringing sound from one of the toms, which is triggering
feedback from a vocal mic. If we pull the tom fader
down, the ringing, and the feedback go away. But we
want the tom to be heard; after all, drums aren't
cheap. Solution; insert a noise gate into the offending
tom channel and set a very fast attack, and short
hold and release times - in other words, a short,
fast envelope that matches the natural envelope of
the instrument. Next, adjust the threshold so that
the gate opens only when the drummer strikes that
particular tom.
By making some fine adjustments to the hold and release
controls we can re-shape the drum's volume envelope
and eliminate the ringing. Problem solved.
This will also ensure that that particular tom mic
will only pick up that particular tom when it's being
played.
Using noise gates on the toms and kick drum in this
way will give you (the sound engineer) a much tighter
overall drum sound and more control over the mix.
"
It should be noted here that when using a noise gate
in this fashion it should be inserted first in the
chain - before any compressor or EQ. The reason for
this is that compressors and EQ can both affect the
dynamics and overall level of a signal, and any changes
to level will affect how the gate's detector circuit
operates making it difficult to get the right threshold
setting.
Now we're happy with the drums
and continue sound checking the rest of the band.
Bass seems okay, but the lead guitarist's amplifier
has a really loud buzz when he switches to the lead
channel for solos. That's going to sound lovely coming
through the PA system when the vocalist is trying
to tell the audience the story behind the slow love
ballad they're about to perform. Solution? Yes. Our
friend the noise gate comes to the rescue once again.
In this case we will set up the gate in a similar
fashion on the lead guitar channel but with a longer
hold time and a much longer release time. That way
the gate won't 'chop off' any sustained guitar notes
should they drop below the threshold. This will require
more careful setting up to get it right, but it's
well worth the effort.
Noise gates can be used on just about any instrument
in a live performance, though most commonly on acoustic
instruments. However, it is very rare to use them
on vocals because of the large dynamic range of the
human voice - it would be too easy for quiet vocals
to go missing - it's better to ride the fader.
Sometimes an effects return can be noisy, especially
if there are any modulation effects in the chain such
as flangers etc. Even digital reverbs can produce
noise that may not be heard on a 500-watt system,
but is definitely audible on a 50,000-watt system.
Never fear, the noise gate is here to keep our PA
quiet.
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