Paul-Andre Perron wrote:

>Beethoven 9th premiere was conducted by Michael Umfaul.  A soloist turn
>Beethoven round to face the audience not because he was unaware the
>performance was over (he was deaf, not blind), but because he was unaware
>of the applause.

Yes, this is the most likely of the various versions of the story.
Beethoven was standing next to the conductor and his name was not Umfaul,
but Umlauf.  The name of the singer who turned Beethoven to the public was
Karoline Unger.

Best,
Joyce Maier