Ask the the person what else you can do to create the most effective communication possible. Deaf people hear nothing. Many people who are deaf can still hear some sounds. And, of course, some deaf people hear nothing at all. A deaf person wearing hearing aids will have no difficulty understanding you when you talk.
Some deaf people wear hearing aids.
But with or without hearing aids , they cannot understand speech . They must rely mainly, if not completely, on their eyes for communication. Deaf people are mute. Many deaf people use their voices and many do not. If you meet deaf people who do not use their voices, they are probably not mute.