Continuity mistake: When Tony is stuck in the tunnel in the prison and is talking to Wolf, there are still several feet of tunnel ahead of him before the end of the tunnel. But when Wolf gives him a push, he is shown coming right out of the tunnel's end.
Continuity mistake: When Wolf and Virginia are talking in the Swamp, a piece of string is on Virginia's shoulder. It disappears/reappears in the following shots.
Continuity mistake: When the Gypsy takes Virginia's hair, she spreads it apart before putting it in the potion. Later, when she goes back to the same potion to curse Virginia, the hair is clumped together in a single lock, not separated.
Answer: It's the sound of his bad luck coming.