When working with vocal and voice in the studio that have a lot of “shh” or “ess” sound in their recorded voice track (sibilance), we often need to reduce that sound without effecting the quality of the voice. This is where the DeEssor plugin can be used.
With the DeEssor plugin you can find the high frequency where this sound hangs out. For example the Waves DeEssor plugin you can identify the frequency where it is found with the sidechain button. Sweep the upper frequency to find just the sibilance. When you find the trouble frequency then reduce the threshold to minimize the sibilance sound. DeEssors are found in most video and audio production / editing programs. Give it a try and play around with it, you will see a improvement in the vocal.