No movie can make incoming fire sound right. It does not matter if it is artillery, mortars, rockets, or small arms, it just never sounds right. It may be because the film crews who conduct the Foley effects have never been under fire, then again live music always sounds different from recorded so maybe you just can't get it right, you get it close.
There is a marked "Crump" sound when a mortar lands. Sometimes you hear the tubes when they launch. That is a far away "POP" and you know it's coming. FNGs don't so they don't automatically scan for cover and then go for it. They stare at you like a deer in headlights until the first one lands,"CRUMP!" Then they would follow you into a pit of burning oil because you look like you know what you are doing. Hell, I'm just trying to keep my big ass from getting "blowed up" before I DD out for the last time.
After the adrenaline rush from the sudden adjustment to total consciousness and then literally running as fast as you can for cover your heart is just racing. Sometimes you eat dirt, sometimes you get to a bunker. Either way you lay or sit there until you get the all clear no matter how it is delivered. Small talk ensues and some of it is just surreal.
Some guys make light of the situation, some go into a silence mode, some are just plain chatty. I get silent and am not in the mood to chat. I just try not to be scared and try to rationalize what is going on. When you are in the bunker the only thing that can hurt you is a big rocket making a direct hit and that is about as rare as a No Hitter in baseball. They do happen but never when you are there. I have heard the big ones and even seen a couple land. Big Lou remembers he and I being stuck behind a convoy that was stopped and me yelling, "Drive! DRIVE!" He was going,"Where, WHERE?" I yelled,"AROUND THEM!" Then the third one hit and it literally punched a hole in reinforced concrete. That was a big assed "WHOOOMP" with a sound of concrete breaking mixed in. Big Lou then went off road and drove like the demon he is. Speed and distance are your best forms of protection in those situations, not hunkering down and waiting.
Bob from Las Vegas remembers when he and I were on an Iraqi base and all of a sudden the vehicle started taking small arms fire (SAF). We both ducked under the dash (like that was going to help with all that plastic protection) and he drove like a demon too. Thing is, it kept happening, the sound also increased in cyclic action when he sped up. That was when our buttholes unpuckered and we realized we were not under fire. We stopped and jumped out to do an inspection. No marks anywhere! What we found was that one of the tires had picked up a piece of trace chain and it embedded in the tire. The tire was whipping the chain into the wheel well and that was what we heard. Scared the bejesus out of us but it was good for a laugh that night at the DFAC.
Charlie remembers when 8 rounds walked into our LSA. I heard the first one land and knew it was close. I pushed a cleaning lady out of the office door and forced her to run. I was right behind Charlie and the second one landed behind us. It was fired from so far away that the angle was almost a flat trajectory. Most of it was backblast but I felt the heat and my ears where ringing. Charlie got hit on the finger tip. That one went,"WHING". I found out later that it landed on concrete and that is what changed the sound. This time there were 4 others in the bunker who beat me to it. The third and fourth rounds hit, really, really close. I looked over at one of my tough guys who was in the bunker. You know the type. They have all the brave tats and wear Harley shirts. this guy was shaking like a leaf and I asked him if he was hit. he just said, "I'm scared shitless. All I can think about is my kids." I told him we were all scared but just stay put. Charlie and I knew we needed to get to the Ops Cell. "Three second break, then we run." CRUMP! CRUMP! "OK, he is firing in sets of two. Wait until after the next set and run like hell." WHUMP, Whump, further away. We ran. I have not run that fast since I was playing football in high school. Once we made the Ops Cell Charlie said,"22 years in the Army and this is the first time I have ever been hit." It was like a paper cut and had one little drop of blood.
I don't know if the movie guys want to come over and sit through a barrage to get the sound right but i know these are all sounds I hope I never hear again.