You can hear a bullet when it goes by your head. A modern jacketed bullet fired at standard velocity creates a sonic boom when it goes by. You hear the little "crack" before you hear the sound of the gun. The first time you hear that sound, it is unnerving, but eventually you get used to it.
Way back in the dim dark ages of my early career, I was on a SWAT Team. We routinely trained to do dangerous things. Our police marksman, we'll call him Steve, was one of the better trained riflemen I have ever know. Standard procedure for us to enter a hostile environment, like a building, was to have Steve provide overwatch for us as we stacked against the door. His rifle was loaded and he was watching out for bad guys. Sometimes we trained for Steve to begin the assault. Steve would fire a round through the door we were standing near. We'd hear the crack of the bullet, then a half-second later the boom of the rifle, and we would enter the building. We trusted Steve literally with our lives and allowed him to fire near us, because we knew that Steve wouldn't hurt us. He was in absolute control of that rifle and he wouldn't hurt us. Trust.
My other team members felt the same way. We trusted each other implicitly. Sure, there were rules of engagement and procedures for handling weapons, but the simple fact was that I had my left hand on the shoulder of the guy in front of me and I was holding a loaded firearm in my right hand. There was a guy behind me with one hand on my shoulder and a loaded firearm in his other hand. When we'd flood the room, each person would break in a different direction and deal with any threats we found.
Many times I would find myself on the edge of an arc of fire, but knew that I was safe, because the guy holding the weapon wouldn't hurt me. Trust.
I taught my sons to shoot, and each the three is better than average with their particular weapons. When we are together on our personal range we observe all the proprieties of safe gun handling. Still, I would enter the arc of fire of any of my sons because I know that they would not shoot me. Not on purpose, not on accident. Never. It wouldn't happen. Trust.
I quit the SWAT team in 1991. I found myself getting a little older, a little slower, my eyesight was a little worse. I knew that my loss of reflex was a simple sign of aging and that I couldn't continue to train with the team because I was slowing down and my aging process might jeapordize the individual members. I was becoming a liability and I owed them more than that. Trust.