Do you see that haystack right around 9000Hz? That’s probably Essing where all your SS sounds are piercing, loud and gritty. Many home microphones do that because it sounds “crisp and professional” (it says here). It hurts my ears and there is a recommendation from the audiobook publishers that you not use a microphone which does that.
There are two DeEssers available, but they’re difficult to adjust and use.
https://forum.audacityteam.org/t/updated-de-clicker-and-new-de-esser-for-speech/34283/1
https://forum.audacityteam.org/t/please-help-with-de-sser/48588/14
Koz