Of all dynamics processors, gates are the easiest to understand and use. Commonly referred to as “noise gates” they are basically a switch used to get rid of the noise you hear during quieter parts of a track by muting the sound. However, they can also be used as an effect, altering the dynamics of the sound.
How Gates WorkNoise is usually hidden by the music signal, as it is normally much quieter in comparison. However, as the signal fades away in quieter sections of the music, the noise can become noticeable. A gate works by switching off the signal when it falls below a certain level (the threshold), muting both the signal and the noise. Various controls set how fast the gate starts working (Attack), how fast it stops working (Decay) and by how much it reduces the level (attenuation).
A waveform of a distorted electric guitar with noise in the quieter sections
The same waveform after gating to remove noise
The Controls
Threshold
The lower the threshold, the more radical the gating and the more unnatural it sounds. As you raise the threshold, you will hear more of the signal, and also more noise will slip through. Conversely, as the threshold is lowered, you’ll find that more and more of the signal is gated out too. When there is a lot of noise, you will need a low threshold setting, and you can raise it with low noise sources.
Attenuation
This control sets the level that the signal is reduced by when the gate is closed, -60dB or more is usually the same as off. With higher attenuation settings you’ll hear some of the noise coming through between the wanted sections of the signal.
Attack and Decay
You can “shape” the envelope of the sound as it starts (attack) and finishes (decay), to change from silence to signal and back again as naturally as possible. If these settings are wrong, you’ll either hear a little bit of noise as the sound starts and finishes, or the sound will be clipped short.
Trigger Input
The trigger input allows you to use a second audio signal to open and close the gate – regardless of the level of the signal is being gated.
Gates as an Effect
There are a few ways to get some obvious effects from gates.
Slow Attack Settings – with a slow attack, a gate will release slowly, changing the attack of the sound. It’s like using a volume control to ‘swell’ into a note. Boss has an effect called “Slow Gear” which does this.Gated Reverbs – using the original signal as a trigger input, the sound with added reverb is gated. This makes for a very controlled reverb sound – allowing huge reverbs to be used which are strictly controlled, without adding to much sustain to the sound.
‘Synching’ Instruments – The common example is locking the bass guitar with the kick drum. Using the bass drum as a trigger input, the bass guitar is gated so that it only sounds exactly when the kick drum does. Another example is using a rhythmic instrument to supply a rhythm to a sustained sound like distorted guitar or, quite commonly to a synth pad. The sustained sound is given a pulse by using the rhythmic instrument as the trigger input.
Guitar Effect Gating
With the better guitar pedal gates, the trigger input can be used for the clean guitar signal so that the gate follows the natural envelope of the clean guitar regardless of the noise level generated by the effects.
Reverse Gates – On some gates, it is possible to reverse the effect of the trigger input, so that the gated signal is only passed when there is no signal at the trigger input. This makes sure that the two sounds are always in counterpoint to each other.
Ducking – Think of when a DJ speaks over music, and the level of the music drops to make space for the voice. This is ducking. This is done by using a reverse gate where the voice is the trigger input and the music is the gated signal. The attenuation is kept lower than usual, as you still want the gated signal to come through – just at a reduced level. It can be used in any situation where you need one sound to make space for another (voice-overs, ducking delays, etc.).
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