As someone who has been in a gunfight, let me tell you that if you are truely fighting for your life, you WILL NEVER HEAR THE REPORT OF YOUR FIREARM! I think the experts call this auditory exclusion, or some other SNS effect on your body when the adrenaline pumps. As for shotguns...you might hear them go off ;P
Cop buddy of mine had his supervisor's Glock 22 go off above his shoulder on a raid, and he never heard him fire because he was so focused on the suspect (shooting at cops from behind a couch). Buddy had conical "flash" and gunpower residue on the left side of his face, said that he never once heard the firearm firing 1-2" from his ear. After the shooting stopped, none of the police had "ringing" ears either.
My under the bed firearms are Wife=Benelli M1 14", Me= M4 with Gemtech Raptor, Beta C, etc.
NOTE to ATF AGENTS: They are both on Form 4 or Form 1.