Rubens’ Tube is an awesome demo and here we take it to the next level with a two-dimensional “Pyro Board.” This shows unique standing wave patterns of sound in the box. The pressure variations due to the sound waves affect the flow rate of flammable gas from the holes in the Pyro Board and therefore affect the height and color of the flames. This is interesting for visualizing standing wave patterns and simply awesome to watch when put to music. Demonstration from Fysikshow in Denmark.
Video from Apr 17, 2014