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Table Of Contents
44 Chapter 4 Dynamic
Let’s back up a bit for a brief explanation: Noise gates often begin chattering when the
level of a signal fluctuates slightly, but very rapidly, during the attack or release phase.
Instead of clearly exceeding or falling short of the Threshold value, the signal level
hovers around the Threshold. The Noise Gate then rapidly switches on and off to
compensate, producing the undesirable chattering effect. If you were able to tell the
Noise Gate to open at the determined Threshold level and remain open until the level
drops below another, lower, predefined Threshold level, you’d be able to avoid
chatter—as long as the sonic window formed by these two Threshold values is large
enough to contain the fluctuating level of the incoming signal.
This is exactly what the Hysteresis feature enables you to do—the value determined by
the Hysteresis slider is actually the difference between the Threshold values that open
and close the gate. This value is always negative. Generally, 6 dB is a good place to
start.
If you’re dealing with audio material featuring extremely sensitive transients, or attack
phases that are critical to the overall sound, you may find it beneficial to have the Noise
Gate open up a tad before the useful signal fades in. This is what the Lookahead slider
is designed for. The program analyzes the signal level ahead of time, and anticipates
the point at which it can open the gate before the signal actually reaches the Threshold
value. When you choose to use this feature, please make sure you set the Attack, Hold
or Hysteresis controls to appropriate values.
When youre working with noise gates, you’ll run across scenarios where the useful
signal and the noise signal have levels that are near enough to be perceived as
identical. A typical example is the crosstalk of a hi-hat—its signal tends to bleed into
the snare drum track when youre recording a drum kit. If you’re using a noise gate to
isolate the snare, you’ll find that the hi-hat will also open the gate in many cases. To
avoid this effect, the Noise Gate offers Side Chain filters.
When you press and hold the Monitor button, you can audition the Side Chain signal.
You can then set the filters to only allow frequencies that contain a particularly loud,
useful signal to pass. For this example, we’ll use the Noise Gates High Cut filter—that
only allows the bottom end and mids of the snare to pass, and cuts the higher
frequencies of the hi-hat. When you switch Side Chain Monitoring off, it will be much
easier to set a suitable Threshold level. This will be a value that is only exceeded by the
level of the louder useful signal—the frequencies that make up the snares
fundamental tone, in our example. Put simply, the Noise Gate only allows the sound of
the snare to pass. Should the need arise, you can follow much the same procedure to
isolate a kick or snare drum within an entire mixdown.