First of all, welcome to both DisBoards and disABILTIES! A couple of personal questions which will assist us in helping.
When you say impaired, please explain in a little more detail. Does he use hearing aids or implants? Is it total hearing loss or partial, does he sign (or read) ASL? Etc.
We have several people who are active in this forum who can give good recommendations, but being able to understand the extent of the impairment will help us help you.