Those speakers in your living room, sitting there, like dull hunks of furniture? What if instead of just playing music, they became a pair of fire-spewing dragons? You'd play a tune, and the pulsing sound waves, usually invisible, would become bursts (or absences) of flame. Walk around the speakers, and not only would you hear the peaks and troughs of the music, you could see them — like fiery breaths coming at you.
Your insurance company might not be pleased, but such speakers exist. They're called "Pyro Boards" — or, if you like, "2D Rubens' tubes." Physics explainer Derek Muller found one in Denmark, built by a team of science demonstrators who call themselves Fysikshow. At the start of this video, project leader Sune Nielsen shows Derek a series of single tones (ewwww... too loud. They hurt my ears). But then, like dragons high on propane, at about 3:40 in, Derek and Sune put some music on — and get jiggy with it ...
As their name suggests, Fysikshow's mission is to keep Danish chemistry and physics students awed, entertained and delighted as they plod through their basic school curriculum. Their pyro board has 2,500 holes. Sound waves move through flammable gas to create alternating high- and low-pressure zones, which, in turn, produce the flame pattern. At their site, you can see other things they've built: their "exploding hydrogen balloon," "nitrogen bomb" and, of course, a "vacuum cannon" that shoots CDs from one dormitory to another through the air.
Derek, meanwhile, just wanders the planet being always awed, entertained and delighted. He used to report mostly from Australia, but thanks to a new sponsor, he's become a world-traveling hobo. When his camera is on, he's Veritasium.