What’s a noise gate…and how do I use it ?

In an earlier tech note that I called “Stage Mud”, I casually mentioned the use of noise- gates to help in taming, what I call, stage-mud. I’ve had many people ask me about what noise-gates are used for, and how to adjust them. So, this time around I’ve decided to elaborate a little bit more on the usage of the noise gate or “gate” as it’s more commonly referred to in the pro-audio world. It is important to point out, that noise gates do not “remove” noise, but rather, they just “hide” it during times of inactivity. The simple analogy I like to use is that of a closet (with a door) that contains an instrument, or drum, or voice, etc. When the door is opened, we hear the sound. Conversely, when the door is closed, we don’t hear the sound (or, at least, less of it). Then, by setting different parameters on the gate, we can effectively decide what sound-level “threshold” opens the door, how quickly the door opens, how long the door stays open, , how quickly the door shuts, and finally, how tightly the door is closed. There are a number of different parameters on the typical noise gate that allow you to determine how and when the “door” will open and close, in trying to hide any unwanted sounds.

In the interest of keeping each of these tech notes short, this installment will deal with
some of the more common uses of the noise gate. We’ll save some of the more in-depth discussion of noise-gate parameters and settings for the next time (Noise Gates – part 2)

First off, one of the most common uses of “gates” is in reducing or eliminating the constant sympathetic-ringing of close-mic.’d toms and kick drums , as well as in creatively shaping the length of a drum’s decay time. By effectively shortening the decay of each drum, and simultaneously reducing or eliminating an adjacent drum’s droning, sympathetic vibrations, the overall sound of the drums is tightened up and clarified in a fairly dramatic way (which makes the overall mix much cleaner).

Secondly, I have found that by placing a “gate” on the insert of an electric guitar- amp channel of the console, I can effectively reduce any hiss and/or buzz that is evident when the guitarist pauses his playing during a song ( or in-between songs). This does require carefully setting the parameters of the noise-gate to insure that none of the guitarist’s ending phrases are inadvertently cut-off by the noise-gate.

These are only two areas that I particularly find gates useful. The use of gates to hide background noise during times of inactivity can be applied to almost any instrument or voice channel, and is a very effective way to make your mixes cleaner and clearer.
Additionally, there are other creative uses of gating that have been used in shaping
sound for “effect” rather than just to eliminate noise (mostly used in recording, though).
For example, gates can be used to create some dramatic reverb decays, and some gates can also be “triggered” by other instruments (with interesting results).

So, I hope this wets-your-whistle regarding the use of noise gates in live audio. Next time we’ll take a more in-depth look at the various noise-gate control parameters and their function.

Happy mixing!

-Michael Grosso, senior audio tech – CCFL

This entry was posted on Thursday, August 6th, 2009 at 2:18 pm and is filed under Gearheads. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.