Alan Baker wrote:
Beryl wrote:
...
Right. And I can push against the hill across the road with my
voice. Not much, but enough to move the diaphragm in a
microphone over there, in a split second. The air expelled from
lungs is never going to make it across the road.

No, sorry. You don't push the hill with your voice.

Of course I do.

The pressure waves contain both positive and negative phases.

So you think that a positive won't push because a negative will be
coming along shortly?

I think their will be no net push, yes.

See the difference: sound waves, no net flow: no net push.

Sound waves, no net flow: more push than I can apply to the hill across
the road.

http://www.tech-faq.com/acoustic-levitation.shtml
http://science.howstuffworks.com/aco...evitation2.htm
http://en.wikipedia.org/wiki/Acoustic_levitation