Roger,

Oops. Mixing periods and frequencies. So the question changes to "And, why are these frequencies in the .033hz to 10hz range (as Roger noted)?"

"The knocking and clicking comes from the shorter period phases which are seen as short bundles of waves. Rumbling would be the longer lasting long period energy."

Bearing in mind that your "shortest" period is 0.1 second -- still a far cry from the note Middle C.

If Russell means the aesthetics, maybe the waves could be manipulated/multiplied so that the dominant one was Middle C.