Clever Halloween Hack Uses Sound Waves to Simulate a Spooky Doodling Ghost

Clever Halloween Hack Uses Sound Waves to Simulate a Ghost

Following a free tutorial that’s available over on Instructables Circuits, Beaven built a 256-transducer array that’s suspended over a dark surface lightly sprinkled with baking powder. The array is not only able to generate sound waves powerful enough to physically blast the powder away, but with enough focus and control it makes it appear as if an invisible finger is actually drawing in the dust.

It’s a wonderfully spooky effect, and one that’s hard to figure out how it works. There’s no visible writing tool making the baking powder move, and no other obvious indicators given the sound waves are invisible and inaudible. Beaven eventually—before Oct. 31 rolls around, we hope—plans to expand the setup to use two side-by-side transducer arrays to create a larger writing surface for a spirit to communicate through, which should allow for longer, creepier messages to magically appear.

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