Oops, I replied too soon…
When I did all the steps above the spectrum shows the frequencies present are completely off. They are all at 20KHz.
I think it is cause by the resampling to 44KHz. A similar thing happens if I resample to 22KHz.
Did I miss something?
Thank you again! 
My guess is that you just changed the track sample rate instead of “resampling” (https://manual.audacityteam.org/man/tracks_menu.html#resample)
very low frequencies are picked up both visually and auditory.
Not by humans.
Visually, yes. You can, as above, measure 2Hz flashing with a stopwatch, pencil, and paper, and there are documented instances of responding to flashing lights, see Flicker Vertigo, but not aurally. We detect low frequency air waves by feeling. So the goal in these experiments is not find headphones what will do 2Hz (good luck with that), but find a mechanical driver that can move your chair or room.
This effect is almost impossible to describe to people who have never been through a slow wave earthquake.
Koz
There is a Binaural beats plugin for Audacity …
https ://wiki.audacityteam.org/wiki/Nyquist_Generate_Plugins#Binaural_Tones_with_Surf_2