I know this is an older thread but I ran across it on google and wanted to add to it for others that see it.
Best way to make T worse regardless of what you're doing? Always be freaked out about T.
Humans can be exposed to higher levels of sound without damage, what does the damage is the amount of time exposed to the louder sounds, gun shots are short burst of sound, yes they are loud but with PROPER PROTECTION, there should not be any added hearing loss.
What causes your T to spike after hearing louder non damaging levels of sound? Focusing in on your T trying to see if it has changed.... Being freaked out about your T and never allowing yourself to be around louder sounds even when properly wearing protection, that's just a recipe for stress and louder T that is all mental...
85db takes 8 hours of nonstop noise to cause damage, every 3db added causes the time to be reduced by half.
121db is about 7.5 seconds of CONTINUOUS sound before damage may start. I'd love to find a study on how a gun shot adds up time wise. You also need to factor in that guns noise is measured at the barrel where the bullet exits the gun, if you are behind the gun you will not be exposed to the full amount of sound that a gun puts out. worst place to be is in front of the gun, (duh) or even on the sides of it near the barrel if shooting at a range with close lanes.
Also about plugs, depending on what frequency level the sound happens at, a 33db rated plug might protect up to 40db, 33db noise reduction is the average across the board. With proper protection (doubling up plugs and muffs) you should be able to block around 40db across the board, after that you need to worry about sound getting in through your body.
Bottom line, if you shoot make sure you wear plugs AND muffs, if possible try to shoot outside. If shooting indoors, just make sure the guy next to you isn't shooting any crazy loud guns. Many people shoot guns and have been shooting guns for many years without hearing loss. Hearing loss and guns normally happens when a gun goes off without protection. I'm that guy that puts my earplugs in before walking up to the outdoor shooting area. To many people have had a random guy shoot off a round early, before everyone has had a chance to get their hearing protection in.