everyone had a hearing aid.
sure, they could understand writings, and they could read. not that they had problems hearing, but they had problems with understanding what others said. so, everyone wore a small translator hooked at the back of their ear so that they could communicate with each other.
but, for every person, there was one person that they could talk to and understand completely without help. in some cases, they could even communicate telepathically. that would be their soulmate.