Respect your language, English speakers! Understand that the written language is above all based at representing the sounds of speech. As such, the word pronounced “mike” and meaning “microphone” should be spelled–can you guess?–“mike”!! Spell what you hear unless customary standards preclude it. Do not adopt the awful spelling “mic” as in the nowadays-common “open mic”. Anyone who understands how English spelling signals pronunciation knows that “open mic” should be pronounced as “open mick”. That is not how people say it. Not yet, anyway.
Of course, I know where “mic” came from. Every microphone jack on any tape recorder or audio component that has been produced in the last fifty years has borne the abbreviated label “MIC”. That is an abbreviation. Now sometimes people do make a funny word out of an an abbreviation. Maybe a few people out there talk about “St. Louis Moe”. But word shortenings in speech naturally are based on the spoken sounds, so the spoken short word for “microphone” has always been “mike”, not “mick”. So, if “open mike” is what you say, let “open mike” be what you write.