English: This picture shows cymatics, the study of wave phenomena, sound, and their visual representations. The patterns shown are created by a laser beam that is reflected by a small mirror onto a wall in my darkened basement. I directed two different coloured lasers, red and green, at the same mirror. The mirror is taped to a balloon which is stretched over the opening of a can which is placed on top of a speaker.

As the speaker plays notes, the sound waves vibrate the balloon, causing two-dimensional standing waves, meaning there are areas of high and low vibration. The mirror on the balloon represents a sample of the balloon's overall movement, as the mirror's angle is constantly shifted by the vibrations. So, any movement of the mirror will change the direction of the reflected beam.

The movements of the reflected beam can trace out interesting patterns such as the Lissajous pattern shown here, which is formed by movement in two directions at different rates. Stable patterns are formed when the two frequencies are a whole number ratio.