This is Water Run through a 24hz Sine Wave

(Video Link)

This is the most amazing thing I've seen all day! Stop and watch this video right now. Brusspup, maker of astounding optical illusions, let water flow past a speaker set to a particular frequency:

Run the rubber hose down past the speaker so that the hose touches the speaker. Leave about 1 or 2 inches of the hose hanging past the bottom of the speaker. Secure the hose to the speaker with tape or whatever works best for you. The goal is to make sure the hose is touching the actual speaker so that when the speaker produces sound (vibrates) it will vibrate the hose.

Set up your camera and switch it to 24 fps. The higher the shutter speed the better the results. But also keep in the mind that the higher your shutter speed, the more light you need. Run an audio cable from your computer to the speaker. Set your tone generating software to 24hz and hit play.Turn on the water. Now look through the camera and watch the magic begin. If you want the water to look like it's moving backward set the frequency to 23hz. If you want to look like it's moving forward in slow motion set it to 25hz.

-via Colossal

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Any frequency with a clean ratio to the camera frame rate should do something interesting, within some limits. If you went with half the frequency, 12 Hz, you could see something more like this (alternating between the two curves each frame), and at a third the frequency, 8 Hz, you could get something like this (cycling over each curve, for a three frame cycle). If you doubled the frequency to 48 Hz, you could get something that looks the same frozen in time, but with twice as many peaks and troughs to the wave. Same goes with higher multiples in principle. Non-integer ratios may work, such as 32 Hz looking like a squished version of the 8 Hz one.

There were a bunch of "could"s and "may"s in there though, because in the end, the pattern may become too messy to be seen due to the thickness of the water (e.g. take one of the linked graphs and imagine the lines becoming really thick), it starting to break up into droplets, or issues with consistency. And for the lower frequencies and ratios that produce a cycling of frames, the brain will pretty quickly interpret cycling more than 2 or 3 frames as smooth motion.

I would do this myself some weekend to double check I am thinking clearly about it... but my old camera does only maybe 0.2 FPS depending on how fast I can push the button and wait for it to focus.

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I imagine the same effect would happen if you set your camera to 30 fps and used a 30 Hz tone.

I also wonder what it looks like in person. I wonder if you shot the 24 Hz at 30 fps if it would basically look "normal".

To address the above question, I wonder if it would look any different at 48 fps, because the tone is still 24 Hz (24 sound waves/second). Maybe it would look like half as many waves? I imagine 48Hz at 24 fps would have the same effect, but double the amount of waves.

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That would depend on your camera's frame rate. The reason it looks so cool is that video frame rate is equal to the number of vibrations per second. That's why you don't see the hose shaking or the water dropping -until he changes it.