Sound Guide - What a noise gate does
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What a noise gate does
If you actually listen to an instrument like a drum you'll find
that its significantly different to what you hear on your CD at
home. You might feel that the kick drum hasn't enough 'kick' or
that the snare drum hasn't enough 'snap' and the reason is that
during mixing, the signal will have been fed through a noise gate
before being used. Essentially this piece of equipment only lets
through loud bits of sound and cuts off quiet parts.
Imagine that you have a door with a spring on it. Hit the door
softly and the door won't open but hit it hard and you'll be able
to open it, letting you through. A very similar thing happens inside
a gate where a signal above a certain strength (the threshold) will
be able to pass through.
The effects of threshold, attack and release on the output signal
of a gate.
There are three main controls that all gates possess:
- The point at which a gate will let the sound pass. Any signal
under this strength will not be let through and so if the threshold
is set too high, it is possible for there to be complete silence.
- The time between the signal reaching the threshold srength and
the gate actually opening to let sound through. Don't confuse
this with delay, the signal isn't paused, the gate just waits
- The time between the signal falling below the threshold and
the gate actually closing to prevent sound passing through. A
higher release time usually produces a softer sound since you
can hear the drum vibrating freely.
Traffic light display
Many gates use a series of three LEDs to indicate what it is currently
doing to the signal:
||Status of the gate
||Input signal is below the threshold point. The
gate is reducing the output level and so nothing will be coming
out from the speakers
||Input signal falling below the threshold level
or rising above it. The gate is using its hold or release circuits.
||Input signal is above the threshold level. There
is now sound coming from the speakers.
Uses of a gate
There are two main uses of a noise gate:
- Change the sound of an instrument such as a drum to give it
more impact. By only letting the loudest part of a drum strike
through into the mix, the drum will sound quicker and stronger.
- Reduce the noise. People talking, interference and other quiet
and unwanted sounds can be removed from the mix by using a gate.
By setting the threshold so that the gate only lets intended sounds
through, there should be silence at all other times. Remember
that it is best to remove noise at the source rather than use
a gate and that a gate can't remove interference down-stream of
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