Read about the deaf-mute that was brought to
Jesus to be healed in Mark 7:32-35

This wasn't an ordinary case of deafness and this
man was unable to speak. Deafness is often caused
by an evil spirit oppressing the auditory nerve.
Often there is nothing else wrong with the deaf
person who would be able to speak if only he could
hear. But since he couldn't hear, he had no idea
what kind of sounds he made when he tried to talk.