Laser cello

This consists of a laser pointing at a light sensor across a gap. The light sensor is connected to a speaker, so if you move an object like a piece of mesh across the gap it will block the light many times a second you produce sound.

You can experiment with moving different objects with different patterns of holes, such as sieves, fabrics, combs etc, at different speeds to see what sounds they make.

You can also make acetates with sound patterns printed onto them and produce more complex sounds. This is how sound was stored on film until digital audio was introduced.

Seeing sound

As well as seeing the relationships between speed of vibration and pitch, and size of vibration and volume, this allows you to see differences in the sounds you make. The different vowel sounds look different, as do 's' sounds, adult male voices produce much more messy waveforms than do children's voices.