From the site:

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 patters 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 colour of flames. This is interesting for visualizing standing wave patterns and simply awesome to watch when put to music. Thank you to Sune Nielsen and everyone at Aarhus for sharing this demonstration with me! And thanks for having me at your conference.

Music by Kevin MacLeod, www.Incompetech.com “Ice Flow”

Pretty sweet!