This highs-only signal is then fed into a compressor’s side-chain input.
This is an input that allows the compressor to react to a signal different from the one it’s actually compressing.
Meanwhile, the non-filtered portion of the signal goes into the compressor’s normal input.
When there’s a burst of high frequencies from an excessive “s” sound, it easily passes through the high-pass filter, goes into the side-chain input, and causes the compressor to attenuate the full-range signal going into the input jack.
The result: the track is compressed slightly at the moment where the excessive sibilance occurred, thereby taming the sibilance.
Theoretically, you could achieve the same result by manually pulling down the fader whenever the harsh “s” sounds occurred, and then immediately returning the fader to its original position—but this would be difficult or impossible (particularly if you’re singing at the same time!).
De-essing, like ordinary compression, makes this process automatic, so you don’t have to worry about it.
In a digital studio, the simplest way to de-ess a track is to put a de-essing plug-in on it.
Figure 7: A de-esser plug-in. Level indicators are always helpful; this plug-in has one for gain reduction (GR) of the sibilance (click to enlarge)
The plug in will probably allow you to specify a threshold for the de-essing compression circuit, and perhaps also a cutoff frequency, which specifies how high the highs must be to trigger the de-esser (Figure 7).
If you don’t have a de-essing plug-in or you’re recording analog, you could use an outboard compressor to do ordinary compression while tracking, and then run the track through a de-essing configuration during mixdown. Or, you could buy a second compressor.
Some compressors have a built-in “de-ess” button which, when pressed, turns the compressor into a de-esser (mid- and low-frequency dynamics remain unaffected). No matter how you employ de-essing, be sure to experiment with various settings to see what sounds best.
Of course, it’s better to avoid excessive sibilance on a track in the first place. With many condenser mics, singing too closely to the mic, or too directly into the mic, can enhance sibilance in an unnatural way.
By backing off the mic and singing a little off-axis—meaning you’re kind of singing past the mic rather than directly into it (Figure 8)—you can achieve a more natural sound with fewer sibilance problems.
Figure 8: Singing slightly past a microphone (white arrow), rather than straight into it (gray arrow), reduces problems with breath noise and also softens sibilance. This mic has a pop filter installed (click to enlarge)
“P-pops” aren’t really related to controlling dynamics, but in terms of the frequency spectrum they are the polar opposite of sibilance, so I’ll mention them here.
A P-pop results when plosive consonants—the sounds of the letters P and B—produce a puff of air that hits the mic diaphragm, causing a low-frequency thump on the track.
At worst, this thump can have so much energy it causes the signal to distort one of the downstream stages—but usually it just sounds annoying and unprofessional, and often it causes a compressor to make the signal “duck” for a moment, which sounds unnatural.
The simplest way to prevent P-pops is to install a pop filter in front of the microphone. These are available commercially, either as a cover that slips over the mic itself, or as a two-layer fine-mesh screen stretched over a ring, which attaches to the mic stand and can be positioned with a flexible assembly.
For a while I used a piece of silkscreen stretched on a wooden frame with good results. And similar to taming sibilance, you can go a long way toward preventing P-pops just by singing a little off-axis.
There’s really no reason you need to sing directly and closely into a mic, unless you’re recording background vocals consisting of pure vowel sounds and you want to make them sound as airy and intimate as possible.
You’ll get a more natural, balanced sound if you back off the mic a bit and sing over it or past it a little.
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