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Experiment shows what happens when water is run through a 24 hz sine wave.

post #1 of 13
Thread Starter 

 

 

A video released on Youtube recently show what happens when water is being run through a speaker that's playing a 24 hz sine wave very loudly. The result is really interesting.

I mostly just posted this to share because I thought that it would interest you guys but if someone would care to explain exactly how this happens that would be cool. :)

post #2 of 13

It is a totally cool video made possible by some clever camera settings ...

 

It's actually an optical illusion (think when a helicopters blades appear to be spinning backwards as a simple and comparative illusion).

 

The sine wav is broadcasting at 24hz ... the camera, in turn, is set to record at 24 frames per second ... creating the illusion of the water pulsating along the length of the various sine waves.

 

I didn't know that at first, had to read an article about it ... but it's still an incredible illusion.

post #3 of 13

24 Hz sampling of 24 Hz (or thereabouts) phenomenon -> we're getting aliasing down to pretty much 0 Hz so it doesn't look like it's moving?

post #4 of 13
Quote:
Originally Posted by mikeaj View Post

24 Hz sampling of 24 Hz (or thereabouts) phenomenon -> we're getting aliasing down to pretty much 0 Hz so it doesn't look like it's moving?

 

I'm not even sure ... I only half way understand how the phenomenon can actually produce such a visual illusion ... 

post #5 of 13

This is a cool experiment, I think I saw Bill Nye do this on his show like 15 years ago too.

post #6 of 13
post #7 of 13

It must be related to the fact that the camera is probably recording at 24 fps?

post #8 of 13
Quote:
Originally Posted by djsubtronic View Post

It must be related to the fact that the camera is probably recording at 24 fps?

Yes, it's because the camera's framerate. If you look at it with the naked eye it won't look as concrete.

post #9 of 13
Thread Starter 
Quote:
Originally Poxxxsted by s1rralo oh View Post

It is a totally cool video made possible by some clever camera settings ...

 

It's actually an optical illusion (think when a helicopters blades appear to be spinning backwards as a simple and comparative illusion).

 

The sine wav is broadcasting at 24hz ... the camera, in turn, is set to record at 24 frames per second ... creating the illusion of the water pulsating along the length of the various sine waves.

 

I didn't know that at first, had to read an article about it ... but it's still an incredible illusion.

 

Quote:
Originally Posted by penmarker View Post

Yes, it's because the camera's framerate. If you look at it with the naked eye it won't look as concrete.

 

This makes me wonder what this would look like to the naked eye.

post #10 of 13
Quote:
Originally Posted by McNikk View Post

 

 

This makes me wonder what this would look like to the naked eye.

Just a wobbly spray.  Not very impressive.  

 

By the way, it's more than must the frame rate, it's also the shutter speed (duration of each exposure).  The actual shutter speed has to be fairly fast for this to work or each frame would be just a blurry image of falling water.  


Edited by jaddie - 3/15/13 at 5:14pm
post #11 of 13
Quote:
Originally Posted by jaddie View Post

Just a wobbly spray.  Not very impressive.  

 

By the way, it's more than must the frame rate, it's also the shutter speed (duration of each exposure).  The actual shutter speed has to be fairly fast for this to work or each frame would be just a blurry image of falling water.  

Yes, that's why it was recorded outside under ample sunlight. If it were to be done indoors then the shutter speed will be too low for a static image.

post #12 of 13

And he'd get water everywhere!

post #13 of 13

Awesome. I love the comment from youtube, "I want to pee like this" 

 

I've always wanted to see sound waves

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