Everything sonic said regarding audibility is true.
In order for sub-harmonics to segment in the AUDIBLE spectrum (In this case the piloting fq is 18K)it must be placed in a space to allow it to resonate against the intermodulating frequency. It need not be in a pressureized atmosphere, but in an area containing sufficient mass to accomodate for the new frequency created when the two collide together since the creating two. They do not sacrafice their magnitude for their resultant. The collision of the frequencys do not occur in the signal stream itself, as said, only where there is open mass for it to be accomodated. If this were true, I imagine it would sound similar to pink sound (which I believe is the collision of all frequencys in the audio spectrum)
This is one of a few reasons that tube amps have a "warmer" characteristic.
That was one smokin question man! Awesome.

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The band is just fantastic that is really what I think. Oh, by the way which one's.........Jethro?

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