))) I may have misunderstood, I think you already know what I was trying to explain?

Yes. I saw this nice animation of it, which shows the back and forth motion of the air molecules, as the compression wave moves along, and the pressure at any point rises and falls.

http://dev.physicslab.org/Document.aspx?doctype=3&filename=WavesSound_IntroSound.xml

This is another video, with cool patterns from sound, based on resonant frequencies of rectangular plate glass, with the sound source coming from the center of the glass.. Note: a different phenomenon than the other video. Standing waves are produced by specific frequencies, as they reflect back from the edges, and cancel at certain points, resulting in no vibration. It doesn't require a special camera to see them. The salt accumulates in areas where the plate is not vibrating.

http://m.youtube.com/watch?v=Zkox6niJ1Wc


Have Fun!
Peter Gannon
PG Music Inc.