Had a monster Black Walnut tree in a small paddack behind my house as a kid. A small shed for the sheep was located underneath. Every fall, that tree would open fire on the roof of the shed. Sounded like a shot! Sheep ran out.... after a bit they would return. Sure enough the wind would shake a few more projectiles loose and the sheep would get scared out of the shed again, and again, and again. They got lots of exercise that way. Hated picking up all those nuts from the 3 trees that were there. That main tree was easily 48"+ DBH.