A voice can sound clear overall but have a few sharp s or sh sounds that become tiring. This is often called sibilance. Do not treat every bright voice as a problem. First decide whether those sounds actually distract at the episode's normal listening level.
Find a useful comparison
Choose a phrase containing the sharp sound and another phrase that already sounds comfortable. Keep the listening volume the same. If you change microphone angle or distance during setup, record both phrases again so you can hear what improved and what was lost.
Avoid selecting settings from an isolated sound alone. A very strong repair can make the full sentence sound dull or change the speaker's character. Compare the result over a complete answer.
If the microphone is close and directly in front of the mouth, a small position change may help. Follow the equipment's instructions and keep the speaker in a position they can maintain naturally.
Prefer focused changes
During an edit, use a reversible process and start with the smallest change that helps. If only a few words are distracting, consider whether a focused level adjustment is enough rather than changing every sentence on the track.
Recheck after voice balancing and final processing. Raising the overall voice or changing compression can make a previously minor sound more noticeable.
Save a version before making a large cleanup pass. Ask a reviewer to compare a short before-and-after section at a comfortable volume. The successful result is speech that remains clear and recognizable without sharp distractions, not a track that has lost all high-frequency detail.