Patrons will experience hearing eerie, ghostly conversations and otherworldly sounds.
The audio source of this blueprint is a Tesla Spirit Coil: a non-powered crystal radio circuit. It is an relatively easy DYI build that can react to radio sources, lightning, electrical interference and even light.
As Tesla himself recounted upon hearing his invention in action:
"My first observations positively terrified me as there was present in them something mysterious, not to say supernatural, and I was alone in my laboratory at night."To give you an idea of what this device sounds like, check out this video when it is reacting to a laser and then a flashlight: Spooky Tesla Spirit Radio
Because the sounds are all produced live, patrons will have never hear the same thing twice. It is also a nice upgrade from prerecorded haunt soundtracks and atmospheric audio.
Instead of a sketch, I'm linking you to a Instructable project with step-by-step directions: "Spooky Tesla Spirit Radio"
This is a low-cost no-brainer that does not require an electricity. You need to add this to your haunt pronto!