Why 'Singing' Sand Dunes Hum Certain Notes

Interesting research. It brings to my mind, and the last paragraph or so seem to point it toward, the same phenomenon that causes the metronomes to synchronize in this video http://www.youtube.com/watch?feature=player_embedded&v=JWToUATLGzs, which is also discussed, about which much levity ensues, but which touches lightly on WHY the synchronicity of the metronomes occurs.

Periodicity in physics seems to hinge on a lot of connected factors, such as physical size, density, resonance.

What I've always wondered is, at the atomic level (maybe even sub-atomic), does the atomic number of a material DESCRIBE the relation of all these factors, and if there IS a direct correlation between atomic number and the physical factors described (The ratio of one factor to another, maybe, and if so, which two or more factors does it describe?) how would we test that?

Maybe the dunes 'hum" at a frequency corresponding to the natural resonance of the base material (silica?).

Carry the thought about atomic number/description of physical characteristics further, and how does that scale into complex molecules made up of two or more "pure" materials (such as GaAs crystals, cut for particular resonant and harmonic frequencies)?

I am guessing about this last part, but it would seem evident that with three or more materials this question would rapidly scale out of control in complexity, to the point that any possible correlative or causitive effects would become unidentifiable, and untestable.

But with a pure material, the postulate could be tested, and with several samples of different pure materials, perhaps enough data could be collected to suggest or refute a strong effect. Then testing with an amalgam of two pure materials might be able to suggest how the effects are manifested in combination.

I'm pretty sure, though, that it would take a lot more knowledge than I have, or have time to gain, and a much better lab than any to which I'd have access, to do this research.

Any takers on this question? Anyone know of research already in progress on it?

They hum because they don't know the words.