Sound waves are a lot more versatile than you'd think. For starters, you can use them to project images onto a bubble and liquefy gummy bears. And now, YouTube scientist and optical illusionist extraordinaire Brusspup shows how sound waves can also be used to manipulate a stream of water into a zigzag shape.
It works by setting the camera's frame rate to match the speed of the vibration from the speaker (in this case, 24fps). The effect can't be seen with your eyes alone—only through the lens of a camera. However, Brussup says that you could use a strobe light to make it visible with just your eyes.
Here's how Brusspup says he set it up:
This isn't the only trick Brusspup has up his sleeve. Last year, he did a similar experiment that uses a speaker to make it look like water is frozen in mid-air.
If you don't want to mess with sound frequencies, some of his other effects are simpler to perform. You can make shampoo "dance" with nothing more than two glass dishes, make an Infinity Mirror with some cardboard and LEDs, and use camera angles to make tea lights look like a 3D fire box.