There’s two. There’s the classic, legacy, senior DeEsser.
https://forum.audacityteam.org/t/updated-de-clicker-and-new-de-esser-for-speech/34283/1
And the newer DeSibilator.
https://forum.audacityteam.org/t/updated-de-clicker-and-new-de-esser-for-speech/34283/199
Under some conditions of severe Essing (SSister SSuzy SsimulateSS) DeEsser would turn Essing into “Effing.” (FFister FFuzy) Not quite as bad, but not natural, either.
DeSibilator changes settings to avoid that.
I use a tool nobody likes: Analyze > Plot Spectrum. Louder is up. Pitch increases left to right. Bass notes on the left. Essing produces a “haystack” in the display in the wrong place. That’s the bump on the right. The beginning and ending of that bump are the two frequency settings in both tools.
The object of successful DeEssing is to smooth out that hump.
No more ice pick in the ear sounds.
Koz