Which part of the ear is most important to protect from damage, and why?

Ear Drum because you need to be able to hear

I do believe it's the "eardrum" you need to protect most, because if you don't, and it is injured or something, then you will be deaf in whatever ear it happens on. It is a very serious injury, and some people say it could cause death, but i wouldn't go as far as to believe that.

I hope the helped!