Let's try to keep it very simple, and think of a gate as a simple on/off switch. Like a simple toggle switch, this switch is either “on” or it is “off”. This switches' normal state is “off”, and when it is “off” it does not allow any audio signal to pass through it. When this switch is turned to “on”, audio passes through it. Once our audio signal reaches a particular level, or “threshold”, our switch turns itself to the “on” position. While this switch is “on”, it allows audio to pass through it. This switch also has a threshold dial, but I could not work that into my “simple switch theory”. But, this is how a noise gate works...... well, somewhat.
As I stated above, our audio signal had to reach a particular level, or “threshold”, in order to turn it self to the “on” position. Some gates react to certain frequencies, instead of volume levels. Make sure that you are aware of what type of gate it is that you are using.
This simple gate, in the image, is either letting audio through it, or no audio at all. What happens when we set the “threshold” to just above a breath level? You guessed it! No audio will pass on through the gate, and on into the amp and speakers. But, when the signal reaches above a breath, the audio passes through the gate. This is handy for a vocalists microphone, as the breaths will not be heard, but the singing will pass through the gate, and be heard by all.
Gates usually are used with one primary function in mind. That function is to rid a track of some “unwanted noise”, weather that noise is direct or via a microphones' bleed. For example, how about a microphone placed inside a kick drum that bleeds in the snare. This might make for trouble when recording the entire kit. Gates are used when recording, after a track has been recorded, and in live situations too!
Here is a cool video that demonstrates a gate, in action, reducing unwanted mic bleed. You see, the other drum kit pieces are entering this particular microphone, and putting a gate across the mic input sort of deletes this “un-wanted” mic bleed.
Getting deeper into gates......
You see, setting the threshold, to the exact frequencies where the other kit pieces are bleeding into the track, and then cutting it back can make them almost disappear.
However, this is not the only use for gates. Another, and very creative use for a gate is to “turn on” an effect, or a series of effects, once a certain threshold is reached. This could be set up to add reverbs, delays, or compressors to a vocal, but only at a precise volume level, and higher. This gate is set up in a “parallel” type of arrangement. This means that the main signal is always heard, and the (gated) “effected signal” is added to the main signal, but only once the gates' threshold is reached. Once the level of the main signal is lowered back down, below the threshold, the (gate) effects are turned off.
If you have done this very trick with gates before, then please let me know about it. Write me an email, or simply post the information on this blog post! I would love to hear all about it!