From personal experience I agree that one isn't typically aware of nor discomforted by a weapon's noise if you're in a stress-alert mode (hunting, shooting incident). This is a function of the brain, an "orienting response" and/or a body alarm reaction (fight or flight response). You're oriented on a critical situation and "habituated out" to the sound of the weapon.

But it is a brain filtering process. It is not a matter of your ear being immune to the injury or protected from it. There is no less pressure on the ear structures (cilia, etc.) than when you're shooting at the range without proper hearing protection. So unless someone can point us to scientific studies to the contrary, I am of the opinion that the injury and ultimate damage to your hearing still takes place.