audible resultant from two supersonic frequencies?

[Richard Moody]

Has anyone experimented with supersonic frequencies and gotten an
audible resultant from them?  If so I would be glad to hear the
details  particularly if there is an easy source of supersonic
frequencies.

---ric

        "He who learns but does not think, is lost! He who thinks
                 but does not learn is in great danger."
              Confucius (551-479 BC)