Although the frequency varies depending on the individual animal, deaf dogs can and do bark. They do not bark in response to auditory stimuli like dogs with normal hearing, but they may bark at visual stimuli or at sounds that they can still hear if they are not fully deaf.
Prolonged or unusual barking can be a symptom of adult-onset deafness as the dog attempts to compensate for hearing loss. Although barking does serve a communicative purpose, it is also an instinctive behavior rather than a learned language; dogs who were born deaf may bark in the right circumstances. Deaf dogs often bark less than other dogs.