There are some conditions, like cranial nerve VII (facial nerve) palsy, where hyperacousis is a symptom. You have a couple muscles in your ear that attenuate so

There are some conditions, like cranial nerve VII (facial nerve) palsy, where hyperacousis is a symptom. You have a couple muscles in your ear that attenuate sound, so it's not out of the realm of possibility that something happened to your father and his hearing improved.