A clue to where would be helpful. There's a real similar spot like that near Halls, Tn. Was an old military airbase from WW2. I hear big booms, at night, around here but there is a "supposedly" closed ammo depot near here in Milan, Tn. Sounds like howitzer fire going on. Doesn't happen a lot but regular enough and there's always military choppers flying over this area and the occasional mil convoy going down the highway, except the humvees and troop carriers are the max fortified ones with blast windows and turrets, etc.., instead of the usual base used type.
So where are you talking about?