Followup question: what about gunners on naval vessels? Being in the loading room when a 16-inch gun went off had too be absolutely deafening.

We recently had a discussion about this: https://www.reddit.com/r/AskHistorians/comments/3lgb6m/guns_are_loud_artillery_is_louder_how_did_the/

If troops did not have ear protection during WW2, when did it becoma a thing? Which army was the first to issue it?

Please everyone, remember the rules. As was explained in the excellent recent meta post on "What it means to post a good answer in /r/AskHistorians":

If you're choosing to answer a question in /r/AskHistorians, there are three questions you should ask yourself first in turn:

   1. Do I, personally, actually know a lot about the subject at hand?

   2. Am I essentially certain that what I know about it is true?

   3. Am I prepared to go into real detail about this?

Do not post hopelessly incomplete answers based on a skimming of a Wikipedia article just because nobody has yet replied after a few hours.

Please be aware that we also have a rule of no personal anecdotes. The reasons why are outlined here.