Each person in each vehicle will have a different version or perspective to relate. Real combat is more audio than visual. In fact, the senses of touch, taste, and smell play a bigger role than sight or hearing. Most Vietnam combat was at night or in heavy jungle vegetation filled with smoke, dust, and debris. With sight already gone or severely restricted, hearing is the second sense to go, leaving a soldier with three senses to experience combat.
High explosives give off toxic gas and vaporize thin metal casings.
Explosions and the impact of small arms transmit their energy through the ground while rounds cutting the air at supersonic speed crack the air which can be felt on exposed skin. It ain't like the movies. In order to keep a soldier's head down, he must be made to feel the rounds either through the ground or the air. Noise alone won't do it. Firing wildly on full auto won't do it.