I'm sorry. You may want to see a neurologist and they can check him and perhaps help you and give you the answers you are looking for.
I copied this for you. There is much more at the link:
Acquired deafness occurs for any number of reasons. Some causes of hearing loss include: Excessive amounts of wax, dirt, hair or other material plugging the ear canal; inflammation or swelling of the ear canal; infections of the middle or internal ear; a torn or ruptured ear drum; loud noise; head trauma; ear mites;
certain drugs; old age.
Caring for your Deaf Dog