IPA: /ˌɔːr.θoʊˈɛ.pɪst/
KK: /ɔrˈθoʊəpɪst/
A person who studies or specializes in the correct pronunciation of words.
The orthoepist helped the students improve their pronunciation in English class.
Orthoepist is formed from "ortho-" (from Greek "orthos", meaning correct or straight) and "epist" (from Greek "epistēmē", meaning knowledge or understanding). An orthoepist is someone who has knowledge of correct pronunciation.
Think of 'correct' ('ortho-') pronunciation knowledge ('epist') — that's what an orthoepist specializes in.
No commonly confused words.