I have only been on a carrier as a visitor...never been on one during a cruise or ops, so no. But ships and aircraft are loud, no matter what they are. And when you've been in the aircraft for 8 or 9 hours, your foamies aren't exactly the freshest and don't provide the protection they did earlier. I swear there is always a fan, pump, or piece of machinery on the boat that you will have to work or sleep next to.
When took my DODMERB at 18, I had outstanding hearing, and I always remember having good hearing. I can tell now that it's not as sharp as it used to be, but I'm still WELL w/in the limits and standards of the hearing loss program and the NAMI standards. It's not something to worry about, just something to be aware of.
Bcgeib...yeah, I don't know, but it sounds like your right on the ringing/foamies trick. Sorry I couldn't help.