Korean · Pronunciation Guide
teul-li-da. The doubled ㄹ is a genuinely long l, so hold it, and the first vowel is the lip-flat ㅡ under an aspirated ㅌ.
teullida
Timing rather than emphasis is the issue: that geminate l genuinely takes about twice as long as a single one, and it is one of the few places where Korean uses consonant length to carry information.
Listen: 틀리다
Free browser voice. Hear it read by a real native speaker inside the LingoDrop app.
전화번호가 틀렸어요.
Jeonhwabeonhoga teullyeosseoyo.
The phone number is wrong.
Listen: 전화번호가 틀렸어요.
Free browser voice. Hear it read by a real native speaker inside the LingoDrop app.
전화번호가 틀렸어요 keeps the long l in the past-tense form and adds a resyllabification at the end, teul-lyeo-sseo-yo. The subject 전화번호가 lenites both of its ㅎ sounds, so the whole sentence runs soft until that l arrives.
English speakers produce a single quick l and the word sounds truncated -- hold it. The aspiration is the other casualty, since a soft ㄷ gives 들리다, a real verb meaning 'to be heard', so under-aspirating here does not merely sound wrong, it says something else.