I got a chance to fire a few guns a while back, and even with ear protection they are LOUD. The instructor warned us to not take our headphones off at any point as it could cause permanent damage.
So did soldiers in these conflicts have ear protection or did millions of veterans return home with damaged hearing/tinnitus?
Your question has been asked before my friend. You will find a few useful answers here: https://m.reddit.com/r/AskHistorians/comments/1xarg5/did_soldiers_of_any_country_during_wwiwwii_use/