I have a very low voice and enjoy singing or humming along with the bass line in music some times. While I was singing along with a song, all of a sudden my monitor started to go a bit nuts and wave. When I stopped singing (or changed notes) it stopped.
I turned to my roommate, "Can you see that?"
"Nope."
It turned out that if I sang a note at the same frequency as my monitor's refresh rate, the image on the screen would start to modulate up and down in a wavy sort of way. But to my eyes alone. Must have been something with the motion of my eyes or my head matching the refreshing of the screen.
I think that's exactly right. Try chewing crackers or chips (the crunchier the better) while looking at an LED clock (like a microwave). Most work, depends on refresh rate. There's a good chance you'll see the same sort of waviness.
Many times at notting hill carnival I have stood in front of a 20 foot tall wall of speakers and had my vision go blurry due to the 30Hz bass tone at 125db making my eyeballs oscillate in my skull.
You head is a resonating structure. If you make it resonate at a frequency that has an interesting relationship to your monitor it will shake your eyes (being part of your head) so that you can see the refresh. (Or at least that's my theory.)
I turned to my roommate, "Can you see that?"
"Nope."
It turned out that if I sang a note at the same frequency as my monitor's refresh rate, the image on the screen would start to modulate up and down in a wavy sort of way. But to my eyes alone. Must have been something with the motion of my eyes or my head matching the refreshing of the screen.