DIFF button: When and how to use it

We can describe Sibilance as an unpleasant tonal harshness at the high end of the spectrum. This can happen during syllables that include the consonants like “S”, “T” or “Z”.

The best way to remove the sibilance from your recordings is to use an audio processing tool like ERA De-Esser. Although the plugin has been intelligently designed to remove sibilance, in the end, it's up to you to eventually decide how much process you need to apply before the result can be considered as acceptable.

The amount of the process can be considerably different from user to user. This is a subjective choice as everyone has their criteria as to what "sounds good". On the other hand, you have to be careful, because going too far on the processing and an "S" can be transformed into "Sh" or even "Th".

Is there an objective reference as to how much processing is enough?

The answer is yes and it's the Diff button!

On the right side of the De-Esser interface, under the Output meter, you can find the DIFF button. Enable it to listen to the "ess" that De-Esser is removing during processing. In other words, you'll hear the difference between the input and the output signal.

What’s the best way to use the DIFF button? 

Enable the DIFF button and adjust the main processing knob, until you listen to a bit of the voice being removed along with the unwanted "S". Turn the knob back a little bit, choose the desired processing mode and there you are! This way, the signal will stay as natural as possible.

A few comparisons between different settings and the unprocessed sound can make all the difference to achieve the most natural-sounding result.