What you Need
Instead of hitting a mechanical resonance in the glass with it moving back and forth, I hit a resonance in the air in the glass (a bit like when you blow across a bottle).
The brown tube is holding the speaker I was using.
and as you can see the paper has taken to the air and has started levitating.
This kept me fascinated for a good while, as I was wearing ear defenders (it is very very loud!), and I think I have worked out what is going on.
The air inside the glass resonates - it moves in and pressure builds up, until the air rushes out again, overshoots and the pressure drops again causing the air to rush back in. The size of this vibration changes with position, it will be largest
The levitation is due to the volume of the sound changing around the glass. It will be louder inside the glass than above it. The paper is moved with the air, so in the louder areas with more vibration it moves more than in the quieter areas. This means that if a vibration moves it from a loud area to a quiet area it is now in an area which is vibrating less so the return vibration will be smaller and at the end of the vibration cycle it will have moved. So over lots of vibrations it will have moved towards the quieter area, and if the sound is loud enough this effect is strong enough to counter gravity and will make the paper levitate.
What to do
What may happen
Why does it happen?
Interesting. I don't think that thinking of air rushing in and out of the glass is the answer though. The only air that will be moving in to and out of the glass will just be the air in the immediate vicinity of the mouth of the glass; I don't think there'll be any air-flow, as such, and the air movement will be more like that of A.C. current rather than D.C. current. Resonation is certainly playing some part though, whether it be the glass putting energy in to the air, and in turn, in to the piece of paper, or whether the air is resonating directly.
This is just a demonstration of the fact that there is no such thing as 'suck'.
just look up Acoustic Levitation on Youtube - you'll find a lot more. this technique is already being used in silicon wafer manufacturing. opus, Wed, 24th Jun 2009
See: http://www.youtube.com/watch?v=94KzmB2bI7s&feature=player_embedded Dr. David Deak, Wed, 16th Dec 2009