In a very articulate way, he is demonstrating what the fellow in the video you posted was trying to say. Given any complex wave pattern, the Fourier Transform can be used to extract the fundamental frequencies that constitute that pattern. This works with sound waves, water waves electromagnetic waves. Incidentally, this Fourier Transform math is what takes place in the subwoofer and active LFR DSPs to create filters that shape the signal.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated