I was looking through Instructables.com and came across this:

http://www.instructables.com/id/Paper-Noise-Maker/

I used to make this when I was really young. You just fold a piece of paper into that shape and flick it really hard. It makes really loud noises and scare the wits out of anybody nearby. Such fun!

And now for a bit of physics while we are at it: How does this work?

Basically, when the centre-fold of the paper gets flicked out, it moves at a very fast rate and pushes the air in front of it away quickly. This creates a shock wave which can be really loud.

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