creating a soundwave particle animation

Hi All,
I have an interesting problem that I'm not sure how to tackle.
I'm trying to create an animation explaining soundwave compression and rarefaction. Here's a link to an online explanatory animation:

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

There are a number of ways to go about it, but what's the most efficient? I tired a displacement map but it distorted the little particles too much. I am now trying to create them by hand which is working but laborious and doesn't off much in the way of adjustable controls.

Any thoughts or hints would be greatly appreciated!
cheers,
bruce w.

Reality is just a collective hunch.