AF’s Weblog

March 4, 2011

Noise Gates Don’t Have to be Boring

Noise gates aren’t as relevant as they were back in the analog days, when hiss was an uninvited intruder on anything you recorded. But noise gates can do some really cool special effects that have nothing to do with reducing hiss. This article shows how to make them a lot more interesting, and throws in a bunch of fun audio examples, too. But first, let’s do some noise gate basics for the uninitiated.

Noise Gates Basics

A noise gate mutes its output with low-level input signals, but higher-level signals can pass through. Following are the typical adjustable parameters found in a noise gate, whether analog, digital, or plug-in.

  • Threshold: If the input level to the gate passes below the threshold, the gate “closes” and mutes the output. Once the signal exceeds the threshold, the gate opens again.
  • Attack: This determines how long it takes for the gate to go from full off to full on once the input exceeds the threshold.
  • Decay: This sets the time required for the gate to go from full on to full off once the signal falls below the threshold. Since decaying signals often criss-cross the threshold as they decay, increasing the decay time prevents “chattering.”
  • Key input: Normally, the gate opens and closes based on the input signal’s amplitude. The key input allows patching in a different control signal for the gating action (for example, using a kick drum as the key signal to turn a sound on and off in time with the kick’s rhythm). Note that in most cases, you won’t find this in plug-ins, only in hardware units.

All right, let’s get into applications.

Selective Reverb

I was using a premixed drum loop from the Discrete Drums Series 2 library, but in one particular part of the song, I wished that the snare—and only the snare—had some reverb. Although Series 2 is a multitrack library, I didn’t want to go back and build up the drum loop from scratch. So why not just extract the snare drum sound, put some reverb on that, and mix it in with the drums?

Referring to Fig. 1, I copied the drum loop in Track 1 to a second track in my sequencer (if you were doing this in hardware, you’d split it into two mixer channel inputs). In the second track, there’s EQ inserted to roll off all the low end, which took most of the kick out of the signal, as well as the high end, to reduce the level of cymbal crashes.

Reverb sélective

Fig.1

The next step was to insert a noise gate in Track 2, and raise the gate threshold so that only the snare peaks made it through (the screen shot shows a Compressor/Gate plug-in, but the compressor was disabled by setting the ratio to 1:1). These peaks fed the reverb, which dumped into the master bus along with the original drums. The end result: Reverb on the snare only, added in with the rest of the drums.

Now let’s take a closer look and listen to some samples…

Kick Drum “Hum Drum”

Here’s a trick for hardware noise gates. Suppose you want to augment an existing kick drum sound with a monster rap kick, like that famous TR-808 rap sound. Here’s a sneaky way to do it:

  1. Set a sine wave test tone oscillator somewhere between 40 and 60Hz, and plug it into a mixer channel module containing the noise gate.
  2. Patch the kick drum into the gate’s key input and set the threshold relatively high, so that the kick exceeds the threshold for only a very short amount of time.
  3. Set the noise gate decay for the desired amount of oscillator decay. Hopefully your gate decay can go up to about 2 seconds, but even 1 second can do the job.

Now whenever the kick drum hits, it opens up the gate for a fraction of a second and lets through the sine wave; the decay time then provides the desired fadeout.

Real Time Manipulation

This real-time performance tip can sound very cool with hip-hop, techno, and other types of music that rely on variations within drum loops. With most loops, the snare and kick will reach the highest levels, with (typically) hi-hat below that and percussion (maracas, shakers, tambourine, etc.) mixed in the background. Tweaking the noise gate threshold in real time causes selected parts of the loop to drop out. For example, with the threshold at minimum, you hear the entire loop. Move the threshold up, and the percussion disappears. Move it up further, and the high-hat drops out. Raise it even higher, and the snare and kick lose their decays and become ultra-percussive.

To read the full detailed article with sound samples see: Noise Gates

 

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June 18, 2010

Vuvuzela Killers

Filed under: Plugin — Tags: , , , , , , , , , , , — audiofanzine @ 8:23 am

How to Filter Out Vuvuzela Noise from FIFA World Cup Games

Let’s face it, unless you are actually in South Africa attending the World Cup and blowing your very own Vuvuzela, you can’t stand the cacophony that’s blaring out of your flat screen TV in the form of a thousand swarming mosquitoes. Luckily, a few plugins have been quickly developed to filter out that so so annoying buzzzzzzzz.

fifa logoYou can imagine my disbelief, Friday night watching the French game opening night of the FIFA World Cup 2010, out on the lawn, on a beautiful summer night, with 100 or so other fans, glaring at a big big screen, with a cool beer in my hand, when suddenly this annoying buzz started pervading my utopia, and never stopped.  First I thought it was a technical error, on the broadcasting station side, or maybe even the projector/mixer that we managed to connect.  Then I thought, as the night progressed, that maybe the beer is getting to my head and there is a swarm of locust about to descend on us like one of the 10 plagues of Egypt.

But no, I asked around, everyone shrugged their shoulders and said: “ah yes, it’s the African plastic trumpet thing”.  What??!! Well, make them stop!  How can we sit through a month of games with this horrible noise in the background.  Sure if I was in the stadium myself, perhaps, a little tipsy, I would think this was the greatest invention to football games, and already start looking into starting a small import business from China.  But I am not.  What are we going to do?  Well, luckily for us, we don’t need to do anything.  Several, enterprising gear manufacturers quickly cooked up some vuvuzela’s noise reduction/filtering plugins, to make it all go away.
Let’s take a look, eh?

Waves’ Vuvuzella Killa

vuvuzela killaWorking in conjunction with a major television broadcaster, Waves say they have crafted a preset processing chain which decreases Vuvuzela noise: The WNS Waves Noise Suppressor and the Q10 Paragraphic Equalizer. Together, they not only minimize Vuvuzela noise, they increase the intelligibility of the game announcers’ play-by-play action and color commentary, Waves assures.

The processing chain for Vuvuzela noise reduction is now available as load-and-use sessions for Pro Tools, Waves MultiRack, and Cubase.

Waves noise reductionparametric eqHow Does it Work?

A combination of dynamic broadband noise suppression and notch filtering are utilized to create the Vuvuzela noise reduction processing chain. Routing schemes and parameter settings were adjusted, contrasted and, compared; multiple instances of each plugin, with different settings, were ultimately used to achieve optimal results, according to Waves.

Yet, the question I would like to pose to Waves is:  With which major broadcaster have you managed to achieve these results?… so I can tune in!

To see more noise reduction solutions see:  Vuvuzela Killers

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