Noise Gates Explained

Noise Gates Explained

A noise gate is a form of dynamics processing used to increase dynamic range by lowering the noise floor. A gate is an excellent tool for removing hum from an amp, cleaning up drum tracks between beats, background noise in dialog, and can even be used to reduce the amount of reverb in a recording.

Parameters

The common parameters for a noise gate are:
Threshold – sets the level that the gate will open, when the signal level drops below the threshold the gate closes and mutes the output
Attack – how fast the gate opens
Hold – how long before the gate starts to close
Release – aka Decay, how long until the gate is fully closed again
Range – how much the gated signal will be attenuated
Sidechain – the sidechain is for setting an alternate signal for the gate to be triggered from, sometimes called a Key
Filters – the filters section allows you to fine tune the sidechain signal.

What’s It For?

The normal use for gating is for removing background noise. An essential tool for clean dialog recording.
Some other uses for gates are gated reverb and using the sidechain to activate other effects.

How To Set A Noise Gate

To setup a gate properly, start with the the attack, hold, and release as fast as possible. Set the range to maximum, and the threshold to 0dB.
Start lowering the threshold until the sound starts to get chopped up by the gate. Slow down the attack time to remove any unnatural popping. Adjust the hold and release times to get a more natural decay.
If you don’t want the background noise to be turned down as much then you can reduce the range control.

Other Uses

Gated reverb was a popular effect in the 80s, mostly because of Phil Collins records.
To set it up, take your drum tracks and send them to a stereo reverb with a large room preset.
After the reverb insert a stereo gate. Adjust the gate settings so that the reverb is cut off before then next hit.
In this example you’ll hear the unprocessed drums, then with reverb, then adding the gate. Listen

Favorite Gates

The classic Drawmer DS201 is a hardware noise gate that is hard to beat.
The gate on the Waves SSL E-Channel is good, simple and effective.
The free ReaGate VST is quite good as well.
Noise gates aren’t very much fun to talk about, but they are a powerful tool that you need to know how to use.

Reverb Explained

Digital Reverb Technology
There are two ways of creating a reverb effect in the digital world, by using mathematical calculations to create a sense of space, which is called Algorithmic. And by creating an impulse response, a snapshot of a real space, and applying that to the sound, which is called Convolution.
Reverb is essentially a series of delayed signals, and Algorithmic reverbs work pretty well to recreate this. Most reverb plugins, stomp boxes, and racks are algorithmic style.

Creating Space And Depth

One of the challenges we face as home studio enthusiasts is creating lifelike music with a realistic three dimensional soundstage. Recording direct with guitars and synthesizers there is no interaction with the instrument and the room, the sound comes out of nowhere and it can be a challenge mixing several of these disembodied performers into something that sounds real. Recorded music is an illusion, you can shape it however you want, these tips should help.

Photo credit: Brian Niesz

Room Mics
Space and depth are tricky things to fake. Your best chance is to capture it with some microphones.
Guitars: When setting up to record electric guitar use both close and far microphones. The far mics (aka room mics) pick up the natural early reflections and reverb of the room. The blend of close and far mics will be the balance of front to back positioning in the mix.
Drums: If you are recording real drums, set up a couple mics as far back from the drums as possible, up in the ceiling corners can work well. You can even try pointing them away from the drums so they pick up only the reflections off the walls.
Keyboards: Electronic instruments like keyboards and synthesizers can be treated in the same way as the guitars. Run them through an amp with some room mics.
If your recording room is not giving you a long enough reverb, you can try compression to increase the sustain.

Re-amping
Re-amping is taking a prerecorded track (usually direct) and running it out or the recording system into an amp or PA and recording it again with some mics in a real space. This is one of the most effective ways of faking it. Rather than using a reverb plugin which tends to push things too far away or is just unrealistic, instrument to amp to microphone in a room doesn't get any more real. Re-amping is the next best thing. Use a re-amp box for the best results.
Guitars: Same as above, run the signal into an amp and mic it close and/or far. If you want to use a virtual amp, you can do it with or without cabinet emulation depending on what you want to do.
Virtual instruments: I have a good friend that programs synths in Pro Tools then runs them through some real amps. He places the amp several feet from a shelf with his record collection and mics the records rather than the amp with a stereo pair of condensers. This makes a virtual instrument sound so much more authentic just by getting some air moving and sound bouncing off things.
Virtual drums: Make a blend of drums and send it out of your audio interface and into a lively room. You get the benefits of MIDI drums but a lot more authenticity by using your own room mics. As always, experiment with mic position for the best results.

Echo
Staying inside the box, you can add echo to instruments which will place that instrument in a space. By echo I mean a short delay effect that gets darker (highs reduced) with each repeat. This will not be an entirely realistic space but it can work well for vocals as an alternative to reverb, it tends to clutter less. A little goes a long way. If you keep this mono the sound will appear to be reflecting off a wall somewhere behind the source.

The Haas Effect
The Haas Effect is a psychoacoustic concept that explains how humans localize sound. In other words, this is how we figure out what direction a sound is coming from. We can fake this with any simple delay and level control. By panning and faking a single reflection on the opposite side we can the illusion of where this sound is coming from. Depending on the level and timing of the reflection, that places the source closer or farther from that imaginary wall and us as a listener. Very interesting stuff. This is also a great way to stereo widen something and this is a staple of my bag of mixing tricks.

Reverb
Finally we get to Reverb plugins, which was likely your first choice for creating the illusion of space and depth. Reverb is very hard to get perfect. The balance of level, reverb time, pre-delay and damping are all critical. We tend to like the sound of reverb and use too much, especially as it seems to hide our mistakes (not the way to fix mistakes). The reverb in a room rarely overlaps the performance or is even noticeable as a discrete element until it's inappropriate for the music. The speed of the music also definitely a factor with regards to how much reverb can be added without becoming cluttered, muddy, indistinct, etc. A huge lush cathedral verb just does not work with speed metal, but a smaller wooden recording room with a short decay will enhance without drawing attention to itself. That's the trick and it can be very time consuming.

There is also the possibility that your music DOESN'T need to be in a realistic space. Clever use of unrealistic space can be the thing that makes your music stand out from the rest. Spring and gated reverbs don't sound like anything naturally occurring but are undeniably effective tools in the correct circumstances. NO reverb, NO depth, and NO space could also be the perfect solution for your musical style.