Listening to natural structures

From livesciene: Eavesdropping on Arches: Rock's Internal 'Hum' Reveals Its Health

I'd love to see what that dataset looks like. They have a few photos, including a spectrogram that shows a lot of energy at 3Hz and 6Hz. Those are totally normal natural vibration frequencies, even in the man-made world.

Now, if you guys just happen to need some help instrumenting the Natural Wonders of the World, just tell me what I have to provide in your grant proposal.