Don't know if it was proven a hoax or not, but I do know that the band Tool added the audio of the call at the end of a song on one of their CDs.
(Tool is the name of the band, "Lateralus" is the title of the CD, "FAAIP DE OIAD" is the name of the song.) More from them here:
Here is a transcript of the call to Art Bell:
"I, I don’t have a whole lot of time. Um, OK, I’m a former employee of Area 51. I, I was let go on a medical discharge about a week ago and,
and... [chokes] I’ve kind of been running across the country. Damn, I don’t know where to start, they’re, they’re gonna, um, they’ll
triangulate on this position really soon. Ok, um, um, Ok, what we’re thinking of as, as aliens, they’re extradimensional beings, that, an earlier
precursor of the, um, space program they made contact with. They are not what they claim to be. Uh, they’ve infiltrated a, a lot of aspects of, of
the military establishment, particularly the Area 51. The disasters that are coming, they, the military, I’m sorry, the government knows about them.
And there’s a lot of safe areas in this world that they could begin moving the population to now. They are not! They want those major population
centers wiped out so that the few that are left will be more easily controllable."
Unfortunately, right at this point, for unknown reasons, Art's studio lost all power and was suddenly off the air, until switching to a back-up
system. I was listening that night, and it was creepy. Even creepier a few years later when I heard the audio again on the CD - deja vu!
Hope this info is interesting, if not helpful.
(Moderators, please delete the quotation if this is inappropriate. Thanks.)