Altitude's effect on pitch of human voice

[Loren Booda]

Does the decrease in atmospheric pressure with increasing altitude affect frequency of sound, such as that of a mountaineer's voice?

 

[Splinter-Cat]

Altitude can do several things to the human respiratory system that can change how one talks. So yes, atmospheric pressure can change the way you sound.

 

[Danger]

That's true, but the atmospheric pressure has as much to do with propagation of the sound as the pitch. The frequency is primarily determined by the length of the vocal chords; the longer they are, the lower the frequency. Thinner air, though, absorbs the energy of the sound before it can go very far.
That's the reason that people sound so 'duckish' after inhaling helium. The change of ambient gas density effectively (but not physically) shortens the chords. That is because the initial vibrations are atttenuated according to the density of the medium that they are propagation through.

edit: Due to more beers than I care to think about, and the interuption of that spamming MF, I think that I screwed up part of this post. I'm sure that my terminology was corrupted. Somebody save my ass, please.

edit: Mentors... I certainly understand why my rather heated response to that spamming f********* was deleted, but why is the object of my wrath still here? Did you check out that link?

edit: Been taken care of by Mentors; carry on...