I'll be honest, 120db was an exaggeration because it was VERY loud, I would not have had a way to measure it in combat gear. Additionally, earplugs are part of a military uniform at a lot of bases so you are required to carry them and the onus would be on you. At that point in time, I was not required to have hearing protection however.

You're not a civilian while enlisted, suing for any reason is not an option in most cases. It's more likely you would file to collect disability in the event of hearing damage after you get out.

Hearing damage should be on the easier to show side; I'm sure they screened your hearing during enlistment, so if your hearing tests as damaged when you're discharged, there you go. Confirming a connection to service if you don't test near discharge might be harder.

You might be surprised... a friend of mine spent 18 months in a tank with a cannon next to his head and has almost total loss in one ear and much lower function in the other... he's had trouble getting VA to pay for hearing aids.

I'm sorry to hear that; I would have expected it to be much easier than some of the stories I've heard about getting coverage for Agent Orange exposure from family and others.

Google "3M ear plug lawsuit".

I hear OSHA also frowns on being fired upon at work

Is it not typical for the military to have hearing protection? My highschool gun club had earmuffs with active noise suppression that would dampen sound above a certain DB level.

It is common and a part of your uniform on a lot of bases i.e. you will get in serious trouble without them.

Depends... apparently doesn't help much if you're in a tank with a cannon a few inches from your head for 18 months.

Or using pneumatic tools for 12+ hours daily for weeks, or spending time underwater with the worlds most powerful sonar