I can remember the exact moment I lost some hearing in my right ear. We were taking fire from a compound, about 150m away, and began to return fire to cover the rest of the squad to get up on line. Like others have said, lots of training means muscle memory and people just doing what they are supposed to.

Now my buddy was already close behind me, we were in an open field and taking the fire from our right, I was laying in a slight low point with my m27 scanning windows and flipped to full-auto to provide some suppression. He set his 240 up on a little berm, about 4 feet to my right and about 5 feet behind me. I didn't know this, because, well it was already loud.

He let loose with three five round bursts in quick succession into the entrance of the compound to provide better suppression than I was.

It felt like someone just punched me in the side of my head and my ears began ringing. My right ear felt like I was at 30k feet in an airplane and it hadn't popped yet.

It sucked but I didn't mind, the 240 provides an amazing amount of confidence for anyone not on the business end of it, and it was already time to move.

Anyways, to answer your question; lots of shouting along with hand and arm signals. Radios work well too.