If your vocals suffer from any of these 3 symptoms, your vocals are too harsh.
- The high end is too piercing
- Your vocal sounds thin
- The high end hurts your ears
So to start, vocals should never hurt your ears. They should sound pleasant, sometimes even euphoric.
If your high end is hurting your ears because it is too piercing you should use a De-Esser.
A de-esser is a compressor that only focuses on the high end. Think about a multiband compressor. Typically if you use a multiband compressor it is split into 4 bands by default. You can typically turn the separate bands on/off as to just employ the bands you feel are appropriate.
A de-esser is essentially just the highest band of the multipressor enabled. The purpose of a de-esser is to make the highs less harsh. It does this by making the piercing qualities quieter and the rounder/fuller features, louder.
Every DAW comes with one, whether you use FL Studio, Logic Pro, Ableton, Pro Tools etc. They all come with a de-esser.
In a situation where your vocals are too harsh, this plugin is perfect. This is what the de-esser was created for.