Concerning hearing loss and gunfire I am reminded of the lyrics of the song " You don't know what you got till its gone " by Cinderella....and it is very true with hearing loss.
Each and every loud noise can cause hearing damage, from plinking on the range with subsonic loads in .22 rifles up to the occasional .30-06 shot at a deer during hunting season.
The effect is cumulative, and it is the combined damage over time that really destroys your hearing. When you shoot without protection, other than temporary ringing in your ears you may think that no real damage has happened, but rest assured, it is has occurred.
The permanent damage will manifest itself years later when you can no longer hear the voices of your grandchildren when they ask you to tell them stories about your youth.
You only get one set of ears ( and eyes ) in a lifetime, don't foolishly put them at risk.
I currently suffer from Tinitus.. Believe me, you dont want any part of it. The doctors could not determin any specific event that caused my hearing damage but I can tell you that I am very protective of what I still have. With me it was probably a combo of Loud music in the 80's.. Loud cars in the 90's and Cheap hearing protection on the range.