But I can't hear the voice I recorded, what should I do?
I see you made a voice set for Korean, but South Korea has been associated in the internal GSX of regional accents to the "en-jp", which is an existing set of voices spoken in English with Japanese accent so, the only way to hear your voices, would be to overwrite the GSX sounds files in that folder. Note that, these will be overwritten by an FSDT Update.
Incidentally, North Korea has been associated with a "ko" language code so, I guess if you fly there, you should hear your voices already.
If you were willing to provide with a complete set of voices ( unprocessed, please ), of English spoken with a Korean accent, for BOTH Pushback and Deice, in BOTH Male and Female variations, we might assign both Koreas to a new "en-ko" code, and make that set official, to the benefit of everybody.
That's what several users did for some languages were we have real voices for. Contact me with a PM, if you are interested in that.