Acoustic Levitation

I ran across the principle of acoustic levitation in another thread. I did a few searches on it, but did not find a link to this article:

science.howstuffworks.com...

Someone that knows/remembers more physics than I do will have to step in and offer some calculations or opinions. Here are some questions...

1) As the size and mass of an object increases, what becomes the limiting factor for the ability to acoutically levitate it? Power? Surface tension or deformation?
2) How much does equipment like what is shown in this video cost? I have no intentions of going out and buying some, I'm just curious. What type of equipment is involved, how complex is it, what level of accuracy and "toughness" is required?

reply to post by Aneta


There is a sort of acoustic levitation that is the mechanism of UFOs or flying saucers
and the like of any shape. This may be the secret to the Tesla method of levitation.
Electrical oscillations at audio frequencies apparently move the + & - charge in
the air and space until the rotation is tuned in one direction to cause suspension.
The - being quicker than the + charge the inertia of charge distribution will soon
be focused - toward the vehicle when the + voltage is applied even as the - cycle
has little effect. Space charge focus effect might be what its call but who knows.