Instruments and Effects

Chapter 4 Dynamics 77
Using the Noise Gate
In most situations, setting the Reduction slider to the lowest possible value ensures
that sounds below the Threshold are completely suppressed. Setting it to a higher
value attenuates low-level sounds but still allows them to pass. You can also set
Reduction to a value greater than 0 (zero) to boost the signal by up to 20 dB. This is
useful for ducking effects.
The three rotary knobs for Attack, Hold, and Release modify the dynamic response of
the Noise Gate. If you want the gate to open extremely quickly, say for percussive
signals such as drums, set the Attack knob to a lower value. For other sounds, such as
string pads, where the signal fades in more gradually, set Attack to a higher value for a
smoother effect. Similarly, when you are working with signals that fade out gradually or
which have longer reverb tails, set the Release knob to a higher value so that the signal
fades naturally.
The Hold knob determines the minimum amount of time that the gate stays open. This
avoids abrupt changes (called chattering) caused when the Noise Gate opens and
closes rapidly.
The Hysteresis slider provides another option for avoiding chattering, without needing
to define a minimum Hold time. You use it to set the range between the threshold
values that open and close the Noise Gate. This is useful when the signal level jitters
around the Threshold, fluctuating slightly but rapidly around it. This causes the Noise
Gate to switch on and off repeatedly, producing an undesirable chattering effect. Using
the Hysteresis slider, you can set the Noise Gate to open at the Threshold level and
remain open until the level drops below another, lower, level. As long as the difference
between these two values is large enough to contain the fluctuating level of the
incoming signal, the Noise Gate can function without creating chatter. This value is
always negative. Generally, –6 dB is a good place to start.
In some situations, you may find that the levels of the signal you want to keep and the
levels of the noise are close enough to be difficult to separate. For example, if you are
recording a drum kit, and using the Noise Gate to isolate the sound of the snare drum,
the hi-hat may also open the gate in many cases. To remedy this sort of situation, you
can use the Sidechain controls to isolate the desired signal using Hi and Low Cut filters.
To use the Sidechain filters, click the Monitor button to turn on monitoring. This lets
you hear how the Hi and Low Cut filters will affect the incoming signal. Now you can
drag the High Cut slider to set the frequency above which the signal is filtered out, and
drag the Low Cut slider to set the frequency below which the signal is filtered. These
filters only allow very high (loud) signal peaks in their range to pass. In our example,
you could remove the hi-hat’s signal, which is higher in frequency, using the Hi Cut
filter, and allow the snare signal to pass. You can turn monitoring off to set a suitable
Threshold level more easily.