Why does my LCD TV look blurry?

When I hum and look at a CRT tv or some LCD clocks, the illuminated screen or display appears to vibrate. Why?

• The vibrating display resembles that of an oscilloscope that hasn't been tuned well. kinda moves in waves. I can speed up the wavelength of the vibration depending on the pitch of my hum. I guess I'm making my head vibrate at a certain frequency to match the electric current in the device? idk. Electrician or techy guy please help me figure out why it happens. oh and i have an super deep voice.

• Answer:

  It's because the low frequency sound waves (which are essentially vibrations through the air) are vibrating your head as they are coming out of your mouth. Your voice box vibrates in your throat to make sound, which in turn causes a vibration in your head. This vibration causes your eyes to vibrate as well, causing vibrating vision. It may be more apparent with CRT or LCD because the screen's refresh frequency may be lower or near the frequency of the ambient lighting in your room, which you can observe by simply picking up the click and moving it really fast in front of your eyes. You will notice that it appears to "blink."