September 15, 2012
These two objects are actually speakers that play a 22khz sound, inaudible for humans. When the waves are perfectly opposed, point are created where no energy is applied which allows the drops of water from floating in the air.
Acoustic levitation is a method for suspending matter in a medium by using acoustic radiation pressure from intense sound waves in the medium. Some methods can levitate objects without creating sound heard by the human ear.
There is no known theoretical limit to what acoustic levitation can lift given enough vibratory sound, but in practice current technology limits the amount that can be lifted by this force to at most a few kilograms. Acoustic levitators are used mostly in industry and for researchers of anti-gravity effects such as NASA; however some are commercially available to the public.