Talking tapes

A British company called Grand Illusions sells "talking tapes" -- strips of plastic with patterns of ridges on them that turn into audio when you scrape them over your teeth or attach them to an amplifier (such as a balloon) and run your fingernail on them.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. Or you can stick one end of the strip to an inflated balloon or a paper cup using sticky tape. The balloon or cup acts as an amplifier, and you can then demonstrate it to anyone nearby.

Source: grand-illusions.comAdded: 19 January 2007