I entered the Army in 71 through ROTC. While in college, I qualified for the Army flight program with excellent hearing. I had to serve 18 months in an Engineer ground unit before entering flight school due to requirements from college ROTC. The Army was just beginning to get results from hearing conservation studies done on WW2, Korea and VN veterans with hearing loss. During the 18 month service in the Engineers, my hearing deteriorated so much due to range qualification with the M16 and 45 cal and other situations, that when taking the flight physical again prior to entering flight school, I was disqualified from the program. Shortly after this time, the Army began issuing hearing protection to every soldier and provided training on proper use. Years later when going thru my retirement physical, the documentation of the hearing loss from 1971-1973 qualified me for hearing aids from the Veterans Administration. In talking to verterans from the Iraq war, they are telling me that some wear hearing protection and some don't. The Blackwater guys have told me they were issued small electronic ear plugs that muffled the gunfire sound, especially when inside vehicles.
So I have said all this to say that the high level of noise caused by gunfire will permanently damage hearing in most people. I'm sure there are some who can survive the loud noise without permanent hearing loss, but they are not the norm. everyone should wear hearing and eye protection when shooting.