The Sound Visualizer and the Chladni Bucket are used to show how vibrations from sound waves are able to create some very beautiful patterns using a few simple pieces of equipment. As compression waves from sound hit a surface it may cause standing waves to form. In the first case, a mirror attached to the surface has a laser aimed at it, the reflected beam is then aimed at a wall and a pattern will form due to the way the surface deforms due to the standing wave. Changing the pitch will cause the surface to distort in different ways causing new patterns to be seen. As combinations of tones are played at the same time, more complex patterns will be formed.
The traditional Chladni Plates are solid metal plates that were originally caused to resonant using a violin bow. Sand or some type of powder is commonly used to show the patterns formed by settling into the areas of little energy (nodes) versus being removed from areas of high energy (antinodes). The more advanced version can use a tone generator and vibrator to excite the metal plates and produce more intricate patterns. In this case, I am producing the same types or standing waves on a trash bag that has been stretched across the top of a 5 gallon bucket. The simplest way to resonant the surface is to simply shout at it at various pitches.