Perhaps it would be best for this article to start with definitions of some terms that we will be using throughout so that even the non-technical of our audio enthusiast readers will not be left behind.
Signal: What you want to hear while recording, like an instrument or a voice or a just a sound.
Noise: What you do not want to hear within the signal, like the spill of sound from people talking in another room or general audio disturbances that may occur.
What is a noise gate?
It’s is a type of audio plugin hardware or software that can be used to eliminate background noise by silencing sound signals that fall below a certain preset DB threshold or allow sound to pass through when the audio signal rises above a preset threshold.
It can be thought of as a sieve that only lets the specified audio elements pass through or as or a gate that opens when there is a signal coming its way and closes when it detects determined noise. The ‘gate pass’ would be the threshold you have set, which should be at the same db level as the sound you would like to hear. Every other audio sound that is lower than the threshold you have set is assumed by it to be ‘noise’ and refused entry.
If both the signal and the noise are on the same threshold, it will let them both in it cannot separate noise from signal if they are both on the same volume or threshold.
How does a noise gate work?
A noise gate blocks noise from coming in and disrupting the actual sounds you want to be heard and it does this by assuming that any sound lower than the threshold you have set is noise and hence unwanted. It’s advisable to experiment before setting the threshold so you will know how loud your instrument or sound is. The plugin will have various controls put in place that help it accomplish this. They are:
A preset level or volume that is to help the noise gate determine what qualifies to be a signal or noise. A noise gate has a feature control the Threshold that is used to set the threshold that would be the determinant for what it would let in or keep out.
This control is used to determine how long the gate stays open before it closes up again. It is usually better to opt for a ‘slow’ release so that rather than cutting off the sound abruptly, it gives it a kind of ‘fade out’ exit.
This is used to set the speed of time it will take the gate to come into effect and act on the sound.
This element is used to determine how long the gate will stay open before the release feature does its work which is to close the gate. The hold control also ensures that the gate does not close up in between short pauses in the audio.
This control determines the amount of attenuation (muting) that will be applied to signals when the gate is closed. Although most times when the gate is closed, signals are entirely muted out, there are times when it would be better off if it were not so. The range feature helps you experiment and apply your specifications.
Noise gates most times have two thresholds; one opens the gate and the other closes gate. So when a signal falls below the ‘close’ threshold and has been blocked out, it has to rise above the ‘open’ threshold before it is let in.
Noise gates are used for a variety of purposes both in mixing studios and on the live scene. They can be used for efficiency when needing to reduce the disturbance of noise from an audio signal and clean the output of it up. They can also be used for creative effect when wanting to intertwine different elements rhythmically to one another through sidechaining.