Basically from how far away the explosions are visible.
Smoke, tracers, cluster bomb detonations and regular explosions all have different visibility range, where smoke and cluster bomb detonations are visible from very far away, whereas regular explosions are not visible until the player is very close, or very zoomed in. Which means you can easily miss that explosions are even taking place, unless they hit something that is destroyed and starts smoking.
I'll attach a screenshot to show. The game was paused when I took the screenshot, the only thing I changed was the zoom.