Plosives and Sibilance

If you’ve ever recorded the human voice with a microphone, you’ve heard them – those nasty blasts from the mouth that quickly ruin an otherwise perfect recording. We call them plosives and sibilance, and they’re the bane of recording engineers around the world. Fortunately, there are ways to minimize and even eliminate these beasts, and it doesn’t matter how much you spent on recording equipment or software.

This month, we’re taming the recorded voice.

First Things First

Plosives get their name from the low-end kaboom created when the talent pronounces a B, P or T sound. These sounds require an extra burst of air from the lungs, which creates a micro windstorm at the microphone. This temporarily overloads the mic and distorts your recording.

Sibilance is an excess of high frequencies created by S and T sounds. While it won’t typically overload the recording chain, the end result is distracting and wears on the listener over time. Both sounds are a fact of life, and the audio recordist has to deal with them. Rather than rely exclusively on post-production processing, let’s apply a little old-school audio trickery up front.

Sibilance is an excess of high frequencies created by S and T sounds.

For a stereotypical voice recording session, you put your best microphone on a stand, have the talent stand close and speak clearly into the mic. That’s fine, but, with a little more preparation, you can minimize the effects of plosives and sibilance. The first step is microphone choice. If you have a $500 studio condenser mic, it seems only natural to use that for the recording, right? Condensers are extra-sensitive by design, which usually gets the best recording, but they’re also prone to accentuating our audio nemesis. When using a condenser, start with a good hoop-type windscreen an inch or two away from the business end of the mic. This will all but eliminate plosives from the mix. Another technique to minimize both plosives and sibilance is to have the talent address the microphone slightly sideways – up to a 45-degree angle. You may lose some intimacy in the recording, but you’ve increased the chances of getting a keeper on the first take.

If a condenser mic just isn’t cutting it, consider a dynamic model. Voiceover artists and talk-show hosts love the ElectroVoice RE-20 and Shure SM-7. These are large-diaphragm dynamic microphones that produce silky-smooth vocal recordings with a minimum of artifacts. If you don’t have access to one of these industry standards, consider a simple handheld dynamic microphone. Legend has it that U2 singer Bono uses a Shure SM-58 to record virtually all his vocals in the studio. This is a $100 microphone that’s available everywhere. Hey, if it’s good enough for him, who are we to argue?

Exploding Plosives

You’ve done your best to record a clean vocal cut, but there are still some leftover plosives on the track. Don’t worry, we can probably get rid of them in post. The first line of defense is a nice, simple high pass filter. This filter’s job is to eliminate all sound below a certain frequency, passing the sound above it unaltered. You’ll find high pass filters in DAW (digital audio workstation, or audio editing software) and video editing software. Unless you’re recording a rich baritone or deep bass voice, it’s safe to start with a cutoff frequency of 70-100Hz. If you hear too much low end missing, just lower the cutoff point till you find a happy medium that minimizes the plosives and keeps the sound intact.

Alternatively, you can attack each plosive instance surgically. Locate your first plosive, and zoom in tight on the waveform. It will be easy to identify – just look and listen for the splat on the screen. Highlight only the plosive, and apply a somewhat more aggressive high pass filter to just that section. Cutoff frequencies could be as high as 200Hz, but tune it as needed. This will minimize the kaboom and keep the rest of the track clean and full. Unfortunately, you’ll have to do this for every instance, but the extra work is worth it. This additional tool may help you identify plosives faster or more accurately, and once you get the hang of it, you might be able to root them out by sight alone.

Excising Sibilance

With the low end tamed, it’s time to address the upper end of the spectrum. For many years, professional recording engineers have used a special tool called a de-esser. It does exactly what you think – minimizing or removing sibilance from recorded tracks. A de-esser works by dynamically compressing – or turning down – the volume in a certain frequency range, only when needed. In the old days, an engineer would patch a compressor into a vocal track, add an aux feed to an equalizer, tune the equalizer to the offending frequencies and patch that back into the trigger input on the compressor. Sound complicated? It was, and you could spend a lot of time dialing everything in just so. Today, it’s much easier. Your DAW software may have a de-esser built in. If so, dig it out, apply it to the track and start tweaking. If not, and your DAW accepts VST plug-ins, Google “Spitfish” and “mda deesser.” These are freeware de-essers that should work magic on your harsh recordings.

Setting up a de-esser is fairly easy. After plugging into the track, open the control panel for the plug-in; we’ll use Spitfish as an example. The first step is finding the primary sibilance frequency. Using a combination of the Tune, Listen and Sense controls, you can identify the offending frequencies and adjust till just those are suppressed. Finally, unclick the Listen button, and adjust the Depth knob until your sibilance is minimized. Every system and plug-in is different, but the controls are similar. It’s up to you to find the perfect balance of suppression and quality sound.

Dial It In

Plosives and sibilance are unfortunate side effects of the recording process. But, using good equipment, a few accessories and some judicious post processing, you can minimize their effect in your projects. Don’t be afraid to experiment with these techniques and toys. Just remember, your audio will be better when it’s over, and the Undo button is just a click away!

Contributing Editor Hal Robertson is a digital media producer and technology consultant.

Side Bar: Hoop Windscreens

Hoop windscreens used to be the exclusive property of professional recording studios. Now you can buy one for $30 or so. But what if you need one today and can’t wait for shipping? Why not build it yourself? Check out our DIY article Do-it-Yourself Hoop Windscreen. With a trip to your local MegaMart or craft store, you can build a fully-functional windscreen for a couple of bucks with some basic hand tools. In just a few minutes, you’ll have a new audio tool to make professional recordings.

Hal Robertson
Hal Robertson
Audio producer since 1979, including studio recording, live sound and broadcast. Video producer since 1994 including shooting, editing and live broadcast. Self employed in production since 1997 and photographer since 2009.

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