Silent Sound

Along the length of the strip is a pattern of fine ridges or lines. Run your thumb nail along the ridges, and the tape speaks. However the sound needs to be magnified, so that you can hear it. One method is to hold one end of the strip between your teeth. Then, when you run your nail along the strip you hear it talk, but no-one else does.

Want.  Reminds me of my love for playing the oven shelf, and the joy of sound that only one person can hear.  (via Boing Boing)