I've heard it twice. Once I was set up on some public ground and had a guy set up a ground blind in a group of trees in the middle of a clover field I was about 100 yds off of. I heard a thwack about 1/2 hr. before sunset and sure enough he got a doe.

The second time I was hunting about 200 yds from my friend and he shot a button in the shoulder and I could here the loud crack.