Answer :
There are many ways someone could become deaf. Maybe they were born with it and somerthing happened when the baby was in the uterus. There could also be because of loud noises (music, being around planes, concerts, ect) The big ones are:genetics, aging, exposure to noise, illness, chemicals and physical trauma. Just some of the one's I told you! :) Hope it helps!
There are many ways some are born being deaf or something happened like lets say someone had a gun and shot it at close range on where you are standing. THat gunshot is louder and can lets just say destroy your ear drums.