get some sound effects going on of random animals and demons and stuff and play it as if its coming from inside the cage, make it really loud and bang on side of cage, but dont start soundtrack or banging until there right next to it.
or get an air cannon and blast it right next to cage, and everytime it goes scream like something is getting you from inside the cage.
Owner of The Fear Experience Haunted House
in Cleveland, Ohio, voted the #1 haunted house in Ohio, and #14 in America by Funtober. The Fear Experience Haunted House was called the premier haunted attraction in northeast ohio by cleveland.com and #1 in cleveland by metromix.