Lesson 56

Advanced De-Essing

De-essing is mostly used for vocals, but let’s not limit ourselves to just that. Once you understand how the various plugins work, you can use them creatively for a wide variety of applications.

Let’s start with vocals. This is what de-essers are designed for. During the mix process, what can often happen is that the sound of “S’s” and “T’s” can get disproportionately loud. This is called sibilance. A de-easer is designed to detect this sibilance, and surgically reduce its volume.

To understand how to eliminate it, first we need to understand what causes it. The original recording might sound great, but during the mix for some reason the sibilance gets out of control. There’s 2 things working together to cause this. EQ and Compression.
Quite often during a mix, the treble will be brought up on vocals. For the most part, this sounds great, except The sibilance has louder high frequencies then the rest of the vocal sound, so that eq boost will make the sibilance more prominent. 
But then, it gets worse by compression. A compressor will reduce the volume of the loud parts, and increase the volume of quiet parts. It senses volume by the size of the incoming sound wave, which is not the same way our ears hear volume. Our ears will hear high frequencies with much smaller waves at the same volume as lower frequencies with a much larger wave. Let’s look at these waves, and the volume in the output meter. These 2 sounds are roughly the same volume, but you can see the wave, and the output of the lower frequency is much higher. Since lower frequencies have more energy, the compressor will react to them much more. When we pronounce an “S” or a “T” there are no low frequencies in that sound. There is very little energy, and as far as the compressor can tell, this sound is low volume. So, the compressor does its job and makes it louder. 
Let’s try it out.
She sells sea shells and sibilance sucks

Here it is with a bit of a treble boost.
Here it is with just a compressor
And here it is with both.

The more prominent frequencies that are heard with sibilance are in the range of 7-9 kHz. The way a de-esser works is it listens for those frequencies. When a vocalist is pronouncing vowels, there’s very little volume in those frequencies, then when an “S” or a “T” is pronounced, there’s a sudden surge in volume in that frequency range. When there’s high frequency sounds that surpass a set threshold, the de-esser kicks in, and is basically a compressor that only reduces the volume of the those frequencies. 
Let’s take a listen to this track, with a high pass filter at 7khz, and a high cut filter at 9khz. You can hear the sudden volume spikes when there’s sibilance.thats what the de-esser uses to trigger the volume reduction. As a matter of fact, you can even use this to make your own de-esser, and it works really well. Create a duplicate of the vocal track, and put this same eq curve on it. On the main vocal track, instantiate a compressor, and sidechain it’s input to the other track that only has the sibilance coming through. If you don’t know what sidechaining is, then check out lesson 4.15 on side chaining.
So, now you have a compressor on your vocal track that only reacts to the sibilance. Tweak the settings with a fast attack, fast release, and set the threshold so your getting about 5 dB of gain reduction when the sibilance kicks in. Congratulations, you’ve made your own de-esser. The biggest difference between this and a dedicated de-esser plugin is that this one evenly reduces the entire frequency spectrum, whereas an actual de-esser plugin will reduce only the high frequencies.

Another kind of home made de-easer within a daw is a multiband compressor. Multiband compressors are explained in detail in lesson 4.9, but in this lesson we will explain it in a de-essing application. As explained earlier, different frequencies have different amount of energy, and a multiband compressor divides the frequency spectrum into several bands, and gives each band its own compressor, unaffected by the frequencies outside of its band. This is the multiband compressor that comes with Logic. I can simply turn off these bottom 2 bands, and use these top 2 bands as compressors. Whenever there’s a spike in volume within a frequency band, that spike will be reduced within that frequency band. 

The challenge with de-essing is to reduce the volume of the right frequencies. There’s a bit of an art to this, and when a lot of de-essing is required it can be quite challenging to make it sound natural. If you don’t have the settings right, It will sound lispy. When it sounds lispy, listen close to it. What frequencies were removed too much? Does it need more high frequencies, or mids? What frequencies need to be added back in to make it sound natural? You can use a combination of these de-easer tricks and tactics to achieve the sound you are aiming for. Generally, it’s hard to get the de-easer set perfectly, and more drastic de-easing will result in more noticeable imperfections. Sometimes when a lot of de-essing is required, it’s good to use multiple techniques to spread out the imperfections and make it overall less noticeable. 

Now let’s take a quick look at a couple other de-easer plugins and how they work. 

Now that we’ve seen how de-esser works on vocals, let’s take a look at how it can be used on some instruments to get a smoother sound.
Acoustic guitar
Tom Drums 
Trumpet in summertime by jake