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What Is De-essing? The Dos and Don’ts of Using a De-esser

by iZotope Education Team and Nick Messitte, iZotope Contributor April 27, 2020
Nectar 3 De-esser module and RX De-ess module
Nectar 3 De-esser module and RX De-ess module

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De-essing is the process of attenuating or reducing sibilance, or harsh high-frequency sounds that come from dialogue or vocals using the letters S, F, X, SH, and soft Cs. 

It’s often a necessary process when mixing audio, but it’s rarely easy—especially when you’re just getting started. Many factors contribute to the complex nature of de-essing, from the way split-band processors can impact the character of a sound, to the manner in which the human voice can change from sibilance to sibilance.

With this in mind, I found it necessary for my practice to develop a list of dos and don’ts. It’s my pleasure to share it with you now. In this article, we’ll discuss what de-essing is, how to use a de-esser, and other de-essing tips.

How to use a de-esser and other de-essing tips:

1. Know your de-essing options: manual clip gain, dedicated de-essers, and dynamic EQ

2. Utilize wide-band de-essing for a more predictable signal downstream

3. Don’t slam your signal with a single, aggressively set de-esser

4. Automate your de-esser; don’t just set it and forget it

5. Trigger your de-esser off high frequencies for more selective de-essing

6. De-ess at the start of a return track to avoid too many highs hitting reverb or distortion

7. Try de-essing instruments other than vocals to reduce harshness

Do: Know your de-essing options

You have a bunch of options for how you’d like to apply de-essing to a signal. The first option, which takes the most time but gives you the most control, is manual de-essing with clip gain or gain automation.

Manual de-essing

To do this, we grab every sibilant part of a signal “by hand” and attenuate it manually, either by separating the clip and lowering the clip gain or by writing some gain automation. This process can often sound more natural than other forms of de-essing, as you’re able to treat each sibilant sound individually. Basically, you look for the recognizable “ess” in the waveform—it often resembles a solid football—separate the ess into its own region, and clip-gain that region down.

Manually de-essing sibilant sounds with gain automation and clip gain
Manually de-essing sibilant sounds with gain automation and clip gain

Manual de-essing also lets you tailor how hard the offensive sibilance hits further downstream processing. This enables you to get the most out of a single plug-in chain: Nothing’s worse than breaking out a phrase into its own track during a verse because it’s not playing nicely with the plug-ins. With the help of tricks like manual de-essing, you don’t necessarily have to!

De-essers and dynamic EQ

The drawback to manual de-essing is the oodles of time it takes. A more common approach to de-essing is to use either a dedicated de-esser plug-in or a dynamic EQ. These tools will both analyze a certain frequency band—typically in the sibilant area of the spectrum—to detect sibilance. When this sibilant audio content crosses a threshold, the de-esser or dynamic EQ can automatically pull the sibilance down.

This is obviously much quicker than identifying sibilant sounds in a waveform and lowering clip gain, and is often transparent enough to suffice. Just be sure you don’t set and forget these automatic tools, lest you end up with unwanted results.

Below are the De-esser module in Nectar 3, the RX 7 De-ess module, and a dynamic EQ node in the Equalizer module in Neutron 3. All three are addressing sibilance in a vocal:

De-essing with the Nectar 3 De-esser module
De-essing with the Nectar 3 De-esser module
De-essing with the RX 7 De-ess module
De-essing with the RX 7 De-ess module
De-essing with a dynamic EQ band on the Neutron 3 Equalizer module
De-essing with a dynamic EQ band on the Neutron 3 Equalizer module

To illustrate the effect of these de-essing features, let’s take a look at some audio examples using audio content that you'd likely process with each of these tools. 

We’ll start with Nectar 3’s De-esser module, which we’ll use on a sung vocal recording:

Original vocal

Nectar 3

We can hear that there are some problematic frequencies with the vocalist’s annunciation of the letter “S,” particularly around 0:05, 0:07, and 0:14. Here’s the same audio example using Nectar 3’s De-esser:

De-essed vocal

Nectar 3

The esses become much less abrasive while still remaining audible, so the recording itself remains uncompromised.

Next, let’s observe the effect of RX 7’s De-ess module on a spoken dialogue recording. Here’s the original audio file:

Original dialogue

RX 7

Once again, the harshness of the esses cuts through the rest of the recording’s sonic content. Now listen to the recording after it’s been processed with RX 7’s De-ess module in Spectral mode (more on the Spectral mode in a bit):

De-essed dialogue

RX 7

You may be noticing a pattern here: the goal is not to remove the esses altogether, but to reduce their presence just enough to eliminate harshness for your listeners. As the industry’s leading audio repair software, it’s no surprise that RX 7 does a fantastic job of mitigating the esses while retaining their natural audibility.

Finally, we’ll demonstrate the use of Neutron 3’s Equalizer to remove abrasive esses from a hip-hop vocal. Take a listen to the original recording:

Original rapped vocal

Neutron 3

While Neutron 3 doesn’t feature a specific de-essing module, we can soften the sharp consonants using an EQ node in Dynamic mode. This means that it will only affect the audio when the recording’s gain crosses the EQ node’s threshold at the selected frequency range. This prevents the possibility of removing content from this frequency range altogether, which would result in an unnatural, synthetic sound. 

Here’s the recording after using a dynamic EQ node:

De-essed rapped vocal

Neutron 3

Voila! As with the first two recordings, we’ve tamed the sibilance of the vocalist’s esses without affecting the integrity of the original performance. 

After listening to these examples, it’s clear that you have several options for delivering a balanced, enjoyable listening experience without having to perform surgery on your recordings. 

Next, let’s take a look at some of the more nuanced aspects of de-essing:

Do: Use wide-band de-essing more often than you’d think

Wide band de-essing pulls down the entire signal when it detects a sibilance. In a way, you can think of it like automated manual de-essing.

Split-band de-essing, on the other hand, splits the signal into two or three bands, and only pulls down a selected range of frequencies when a sibilance triggers the compressor. This makes the process a momentary dynamic EQ—or multiband compressor. So, for a split second, your split-band de-esser is affecting the timbre of the signal in a way that you must now account for, as it will be suddenly equalizing the signal, rather than decreasing its overall level.

But chances are you’re going to want to use other processes to equalize your signal; these processes could very well be muddled by a split-band de-esser: it’s harder to get an idea of what to do consistently when a specific element—say, the frequency band of an ess—is constantly changing in response to a threshold. It’s one thing if the totality of the signal changes in amplitude, it’s another if only a small band of its harmonic makeup shifts. For this reason, I tend to favor wide-band de-essers over split-band, especially if they’re the first processors in the chain.

This isn’t to say that I avoid split-band de-essers. I don’t—and neither should you. They make wonderful additions to high-shelf boosts on a vocal, either before or after the EQ. But I tend to use them as a secondary de-esser, and if brightness is not something I’m trying to add overall, I tend to favor the wide band processes alone.

If you’re interested in trying out some split-band de-essing to hear the difference, the De-ess module in RX 7 has a “Spectral” option, which allows for multiband sibilance control.

Spectral mode on the RX 7 De-ess module
Spectral mode on the RX 7 De-ess module

The following video shows this Spectral option in action:

Note: This video showcases these de-essing techniques using the De-ess module in RX 6. The same techniques are possible with other de-essers like the RX 7 De-ess module, which is largely identical to the De-ess module in RX 6.

Don’t: Hit the process hard, all at once, with one de-esser

We’ve all seen it, folks—an online tutorial where someone de-esses a vocal with all the grace of a sledgehammer. In doing so, the mixing engineer invariably causes the singer to sound like he or she is spitting out sibilance. I call it the Sylvester effect, in honor of the famous cartoon cat.

Friends, don’t do this. We know it’s often better to move the effectual needle one small process at a time, using many tools in series for a cumulative, more natural-sounding result, Often this approach beats using one plug-in in a heavy-handed manner.

In my experience, this principle is especially true when de-essing. A little manual de-essing here—half a dB, maybe a dB—followed by some further de-essing of another decibel or two—with other processes between—is far more likely to get you there without overkilling the vocal—without taking away its natural presence. 

Don’t: Set it and forget it

Because of the unique variance of the human voice—unique, even from syllable to syllable—don’t think you can set a de-esser and walk away. You can’t expect it to act consistently across all esses. Maybe the singer stepped away from the mic, turning her head off axis; maybe the singer put his tongue in a different mouth position; whatever the case, there will be different esses from time to time.

Here, the answer is automation. Either you change your de-esser’s sidechain parameters, or you set up an entirely new de-esser, automating it to engage on a specific part of the song. Whichever method you employ, expect to change parameters every once and a while, as the human voice is not a one stop shop situation. 

Don’t: Give up on a pesky vocal without trying this trick

There are so many times that I can’t tamp down the specific, aggravating timbre of an ess with a conventional de-esser. Years ago, before I realized I was using the wrong tool for the job, it made me want to pull what’s left of my hair out.

I’m talking about nasty bunches of frequencies that hover down lower than you’d expect—in the 4–6 kHz region—frequencies that sometimes sound horrible on certain sibilated phrases. A conventional de-esser might not work, and here’s why:

While a sideband selector usually can analyze this band, this band might not actually be appropriate for triggering the de-esser. It will pull down more than the esses, in other words. The detecting frequencies—the frequencies that carry the majority of the esses—and are therefore better for “tuning” the de-esser)—these often lie higher up the spectrum, in the 10–12 kHz region.

Here you have two choices: You can separate the sibilance to a new track and EQ it, making sure it goes into the same chain for further downstream processing. This can cause artifacts due to switching between regions if you’re not carefully. Enter the other solution: 

You can use something like a dynamic EQ node in Neutron 3’s EQ. It works as follows: call up a node in the upper, more ess-located frequencies of 10 or 12 kHz, then set the gain to 0 dB—so the band is not actually doing anything. Next, set up a dynamic EQ node lower down, at 4–6 kHz, where the offensive frequency is. After that, assign the internal side-chain of that 4–6 kHz band to the higher band—the one with 0 dB of gain. Yes, it’s bit tough to explain on digital paper, but it looks like this:

Internal sidechain de-essing with a dynamic EQ node Neutron 3
Internal sidechain de-essing with a dynamic EQ node Neutron 3

In setting up a dynamic equalizer in this way, you can tamp down those harsh frequencies at exactly the right moment, because they’re sidechained to the higher ones, where the ess of the sibilance is located.

Do: De-ess your reverb and distortion effects

If you’re planning on sending a little of your vocal to a reverb or a distortion effect, experiment with de-essing the vocal, even a second time, before hitting the verb or the exciter. A bright vocal may be too much for the reverb or the distortion process, calling too much attention to the onset of the ambiance or the harshness of distortion. Putting a de-esser before these processes can mitigate some of the unintended side effects.

Do: Experiment with de-essers on other instruments

This is a bit of a bonus tip, but still, I’ll share it: de-essers are not just for vocals. Because of the innate harshness of many instruments—and because of the way some de-essers can respond quite smoothly—they can be great, band-specific remedies for guitars and drums, particularly overheads.

For guitars, this is especially true on electric axes that make use of amplifier simulators, as emulations often reveal their fakery in the harshness of the high-midrange. Slap a de-esser down around 4 kHz or so, and you may be able to get more authenticity out of a fake amplifier.

Likewise, if you have too much cymbal splash in the overheads—to the point that it’s just tearing your head off—give the de-esser a go. You may find it does the trick in softening the blow without sucking all the life out, as a static equalizer might.

Note: This video showcases these de-essing techniques using the De-ess module in RX 6. The same techniques are possible with other de-essers like the RX 7 De-ess module, which is largely identical to the De-ess module in RX 6.

Conclusion

In our efforts to master a technique, sometimes we apply de-essing where it’s not needed. Sometimes we overdo the process just to prove that we have a handle on it.

De-essing must be carefully employed; not all vocals require it, and sometimes, a prolonged experience editing the voice before the mix makes us overly sensitive. Mixing immediately after editing can lead us to de-essing too much.

Thus, along with this list of do’s and don’ts, always remember the context of what you’re de-essing. If you’ve spent an hour editing a vocal, give your ears a rest before mixing it, even if it’s just five minutes. If your vocal sounds good against a reference without the de-esser, maybe you don’t need it. Always remember that context is key in achieving your best ess.

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