I've shot contemporary shotguns and rifles (very stupidly) without hearing protection. One time I shot skeet for an hour, my right ear had substantial hearing loss for 4-5 days following, it was like I had water in my ear for 4 days.

I was just watching a documentary about WWI and it showed a clip of a soldier firing a belt fed machine gun with no hearing protection, and all I could think about were his ears.

I know they didn't have much in the way of hearing protection in WWI and WWII. The majority of soldiers who returned must have had some pretty serious damage to their hearing with the continuous machine gun and rifle fire.