To put it very simply, a gate is a processor that only allows signals greater than a specified amplitude to be heard and signals less than a specified amplitude to be reduced or silenced. This processor is mainly used as a tool for removing unwanted lower level signals like bleed and noise from a track when the desired sound is not being played. A very common example is with a drum. When you place a microphone on a snare drum, that microphone will predominantly pick up the sound of the snare but it will also pick up the sounds of the other drums and cymbals to a lesser degree.
As you can see and hear, there is a significant difference between the amplitudes of the snare vs. everything else. This volume difference is one of the main aspects that determine the potential quality of the gate’ process. Before we get into how to use the gate, lets look at the controls.
Attack – How quickly the gate opens once the signal becomes greater than the threshold.
Hold – How long the gate remains open once the signal becomes greater than the threshold.
Release – How quickly the gate closes once the signal becomes less than the threshold.
Range – How much signal level is allowed through when the gate is closed.
These are the basic controls that are found on every gate. Some gates have additional controls that give you an added frequency dependant element of control. This process is not triggered by the signal breaching the threshold but more accurately by the amplitude of any frequency range or bandwidth that breaches the threshold. This is very useful when it comes to gating drums because each element of a drum kit has a different main frequency bandwidth. For example, the kick mainly occupies a lower frequency bandwidth than the snare. It is this difference that this feature gives you control over. This control happens through a process called “side chaining” which I will cover in more detail in a later post.
Another way to look at the gate and it’ controls is to look at the envelope that the gate creates and how it interacts with the envelope of the sound that it is applied to.
Envelope Created by a Gate
It is important to understand that even though the primary purpose of the gate is to remove noise or bleed, it can only remove or affect the noise or bleed that occurs when the gate has not been triggered to open. Any noise or bleed that is present at the same time as the triggering signal will be heard as long as the gate is open. You should think of the gate as an automated volume controller. When the gate closes it is similar to turning the volume knob all the way down or fading the signal out and when the gate opens it is like turning the volume knob back up to its original level or fading the signal in. It is because of this turn up/turn down or fade in/fade out function that I categorize the gate as a horizontal processor. The gate will have the majority of it’ affect on the beginnings and the ends of a desired sound.
Next, lets look at how the gate interacts with the envelope of a snare.
The Gate’ affect on the Snare Envelope
The following diagram represents a snare being gated with the following settings.
Threshold – Set just above the sustain level.
Attack – Set to a fast value of (af) and set to a slow value (as).
Hold – Set to a value of (h) that extends into the snare’ release.
Release – Is shown with two different values, a fast value (rf) and a slow value (rs).
The top diagram shows the original snare envelop in thick black lines and the affect that the gate has on it in red dotted lines.
The bottom diagram shows what the gate is doing to the volume of the snare track.
By looking at the diagram you can see that anything prior to the snare signal passing above the threshold is fully attenuated including the leading quiet portion of the snare. This is because it is the signal’ crossing of the threshold that triggers the gate to (open) where the speed at which the gate opens is determined by the attack. As you can see this causes a slight change in the natural attack of the snare. For the most part, this is not too big of a deal but if the attack of the gate is set to be too long, the natural attack of the snare will not be heard at all.
The next action to be triggered is for the gate to (close) when the signal passes below the threshold where the speed at which the gate closes is determined by the release. If we were to only have the gate to operate on these two points with very fast attack and decay times then the only thing that we will hear is the red shaded area between the (open) and (close) points. As you can guess, this does not sound anything like the original. You can adjust the release time from this point but since the release is a gradual reduction in amplitude, it will have an affect on the natural sustain of the signal. In order to retain this natural sustain you would need to delay the trigger for the gate to close, this delay is what the hold does.
Every naturally occurring sound will typically have a duration that is longer than it’ initial attack spike or transient. Because of this, it is pretty safe to allow the gate to stay open for a bit even though the signal has passed below the threshold. By keeping the gate open it allows the snare’ sustain to pass through unaltered and forces the gate’ release to be applied during the snare’ natural release where the affects of the processing will be less noticeable.
In the diagram I show two release times both of which are shorter than the natural release of the snare. Typically when gating a snare or a drum in general the goal is to match and retain the signal’ natural release and have control over all other leakage sounds after that. Controlling the leakage is what the range does.
The “range” controls how much of the leakage or bleed signal is heard while the gate is closed. If the range is set to zero, then nothing will be heard when the gate is closed. As you increase the range you will begin to hear more of the bleed signal until the bleed is back to it’ original volume.
Setting the Gate
The first thing that you need to set is where the threshold should be. Start by setting the attack, hold and decay to the fastest settings (lowest value) and set the range to it’ lowest value. This will allow you to only hear the signal that passes above the threshold.
Try to set the threshold as low as possible, where the gate is only being triggered by snare. If you hear even the slightest tick of anything besides the snare triggering the gate then you need to raise the threshold a little.
Most of the time you wouldn’t have to adjust this parameter to a slower setting but occasionally with a fast attack you will hear a tick every time the gate opens. This happens because there is too rapid of a change in amplitude similar to a bad edit where a waveform doesn’t begin on a zero point.
When processing percussive instruments it is a good idea to think about the rhythm of the song. With this in mind, try to set the hold to a value that is in time with the rhythm, long enough to contain the sustain but not so long that you hear the natural release of the snare. (I like to think of the sound of a dry 80’s electric snare hit)
With this parameter you are bringing the natural release of the snare back in. Try to set the decay so that the gate closes just before the first hit of the unwanted sound.
At this stage the gated snare can sound a bit unnatural because of the sudden start and abrupt end. By allowing a small amount of bleed to be heard will greatly improve the sound of the snare’ natural release.
The gate is such a simple yet highly effective tool. By using a gate to clean up your kicks, snares and toms you can greatly improve the clarity of your drums. Back when I was figuring out how to use the gate, I would experiment by mixing a song without using gates at all and take note of the limitations, challenges and the sound. I would then mix the song again using gates and take notes. What I found was that despite the clarity benefits, there were some songs that sounded better without gating and some that sounded better with and just as I would tell my students, knowing the theory is useless without practical experience, so go forth, experiment and form your own opinion.