The red noise tin makes noise. Inside the tin is a transistor noise source and a light-controlled analog filter that filters the noise. There are a couple of knobs for rough center frequency and Q, and some light sensors (photocells) that control the exact filter frequency and the volume. The "speaker" is just a piezo-electric element soldered to the lid of the tin.
The red noise tin can be played by using your hands to vary the amount of light that falls on the sensors. It can also just sit in a room somewhere, and it will play itself as the light in the room changes (shadows move, people pass by, etc.)