The day before yesterday I posted a Youtube video of couter battery artillery fire. Fortunately, we own all the big stuff.
Today I found an older video from Afghanistan that captures a mortar attack on a US FOB. **NSFW -- Language**
Mortar attacks in Afghanistan and Iraq on FOBs were sometimes a day to day occurance, and one never forgets that sound of those incoming rounds.
On Camp Ramadi, there was this supposed early warning system that would broadcast "INCOMING INCOMING INCOMING" across the whole place via loud speaker in what was perhaps the most terrified voice imaginable. 99% of the time it would be a false call, and often a mortar or rocket would impact on the facility moments after the "ALL CLEAR" signal was given. I would joke that you were never safer than when the INCOMING call was sounded.
Now, pray for our troops.
Update: This video has the scary man INCOMING voice right before a mortar impact.