Noise gate controls
- The Threshold control sets the level at which the gate will decide
whether to open or close.When the signal is above the threshold, the gate will be open. When it is
below the threshold, the gate will be closed. With the control set at minimum,
the signal will always be above the threshold, even when only noise is present.With the control set to maximum, then the signal will never rise above the
threshold and the gate will be closed. Somewhere in between there will be
an optimum point where the wanted signal gets through, and the unwanted noise
is blocked. It is important to make sure that when the musician plays, the
first note gets through, right from the initial attack.Also, when the musician stops, the decay of the last note is maintained adequately
before the gate closes. There are controls other than the threshold control
that influence this, but the threshold must be set as precisely as possible
before continuing. - The Range control sets the degree of attenuation when the gate is
closed.Noise gates are commonly set to maximum attenuation unless there is a good
reason to do otherwise. On a single signal, the gating effect will be obvious,
but of course it should not be so in the context of the entire mix.If the opening and closing of the gate is still noticeable, then the range
control should be set to achieve the best compromise. - The Hold control sets a time period during which the gate will remain
fully open, even though the signal has just dropped below the threshold.If the hold time is set to zero, when the signal crosses the threshold there
will be a period of uncertainty when the gate doesn't know for sure whether
it is supposed to be open or closed and it will change state rapidly a number
of times, causing what is sometimes known as 'jitter' (not to be confused
with digital jitter).The hold control is usually set to the minimum value that causes jitter to
cease. (Some gates alternatively have a Hysteresis control. This sets
a separate threshold for signals that are rising in level than for signals
that are falling in level. Having a variable hysteresis control is actually
better than having a hold control. - The Attack and Decay (also known as Release) controls
are used to shape the envelope of the sound as it comes in and goes away with
the object of changing smoothly from silence to signal, then signal back to
silence, without cutting off any of the wanted sound, nor letting any noise
get through. - Stereo Link is a function only used when applying a twin channel
gate to a stereo signal.An example would be an instrument played through a noisy old analog chorus
unit (because you just like the sound!). When this is on, both channels are
forced to open and close at the same time.If this is left off for a stereo signal, no matter how carefully you set the
threshold controls the channels will change state at slightly different times.
You won't believe how dreadful it sounds until you try it.
David Mellor
David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Adventures In Audio.
