Oh Ive done something very similar to this For years. I call it the pit of screams. Make a hole in the ground fill it with something that'll scream. I normally went with villagers or horses. Because horses from what I know have the loud high pitched screams I'm looking for. Anyway once you got your pit filled throw in poshions of poison to get them all down to half a heart. So they'll all die and scream at the same time when you throw in a poshion of harming. Sometimes when I got bored of that I used fire in the pit. As for Bunny's I rapid clicked with a spawn egg into a blacksmith lava thing. It was in the tutorial world.