“If they can sing low enough, about thirteen octaves below middle ‘C,’” you quoted from a note from Stephen Wilson, Ph.D., of Applied Intelligent Systems in Ann Arbor, Michigan.
As middle C is 262Hz (cycles per second) in frequency, 13 octaves below that would be 0.032Hz, which is not only inaudble, but hardly qualifies as ‘sound’ at all, being more like a bump every 30 seconds!
I think he’s kidding, too, but then I don’t know any Michiganders.
M.