Actually, it’s not unheard of for hearing to return mostly, if not fully. A friend in high school blew out an ear drum(or whatever it is when blood starts running out your ear and you can’t hear anything) with a car stereo. Sixteen 10” subwoofers may have been excessive. As I understand it, it’s a bit of a dice roll. Good luck.
It depends on the type of hearing loss. I think your friend had a conductive hearing loss, but may have done some damage to his cochlea hairs as well. Without an audiometric test before and after, it is tough to say which is which.
Conductive Hearing Loss
This is damage to your outer ear, ear drum or ear bones. It is normally curable to the point that it will restore hearing and sometimes will require surgery to fix.
Sensorineural Hearing Loss
This is a loss of hearing in the Cochlea, which looks like a snail shell that is filled with internal hairs to conduct sound to the auditory nerve and then to the brain.
Generally, sensorineural hearing loss cannot be treated. There are some advancements in cochlear implants, but the technology is currently not as adequate as the biological cochlea in humans.
Temporary Threshold Shift - It is when you are driving home and you have the radio on, then the next morning you get into your car and radio is too way loud. What happens is the Cochlea hairs that coduct sound to your nerves to your brain basically lay down. This does prevent some damage. They can be damaged and the hearing loss can be imminent in the future as the hairs age and/or die.
Hearing Loss - Is when your hearing changes, the cochlea hairs that conduct sound break or die generally from noise or age (presbycusis), but can be from chemical exposure to ototoxins. After the hairs break or die you lose the ability to distinguish sounds especially at the higher pitches. You may be able to hear your friends alright, but your grandchildren may be difficult to understand what they are saying. It will sound like mumbled jargon. It is not something that you want to go through.
