Hello, I'm really new to building circuits, and I need some help with an idea I have. I read in a book that a high pitched siren is hard to locate, the sound seems to come from everywhere. How could I build a Circuit that could activate a toy siren via a timer of some sort, lets say after 30 mins, and then shut it off after the siren has sounded for 30 seconds. The siren could be hidden in a classroom, go off and make everyone jump, and then be retrieved at a later time. Thanks!