The experience of "hearing" one's voice in their head, often referred to as inner speech or internal monologue, can vary from person to person, including those who are deaf. For individuals who were born deaf, or who became deaf at a very young age and have never experienced auditory input, their inner speech may not involve auditory sensations as it does for people who have had exposure to spoken language.
Instead of "hearing" sounds in their head, a deaf person's inner speech might involve visual imagery, sign language movements, or some other sensory modality they use for communication and thinking. It could be in the form of hand movements simulating signing or written words or even feelings and emotions rather than sounds.
It's important to remember that the way we perceive the world and engage in internal thinking can be influenced by our individual experiences and how we've learned to process information. The concept of inner speech can be complex and may differ from person to person, regardless of their hearing abilities.