Why does helium make your voices high pitched?

[Deadpangod3]

Name says it all, its a question that's been bugging me for the past day.

So,

Why/how does helium change your voice?

[Guest Brody_Peffley]

Its because helium is lighter than air and changes the vocals coming out of your mouth, It also had to do something that helium changes the sound frecuency in the vocal cords.

[Tex_NL]

Helium is significantly less dense than air. As a result, the speed of sound is much higher in helium. By inhaling helium you are effectively increasing the speed of the sound of your voice.

If you would inhale a heavy, dense gas like Sulfur-hexafluoride you would get a low pitched voice.

But fore more details I'd suggest you try this link.

Edit: Ninja'd

[DonLorenzo]

And if I'm not mistaken, if you were to be in a full helium atmosphere (not recommended, slight risk of suffocation!) voices would sound normal again. It's that the fast traveling sounds (generated in the helium-villed voicebox) 'bunch up' when they hit regular air and slow down, thus increasing the pitch. But that's just me guessing, could be wrong about that.

edit: just read this: http://www.straightdope.com/columns/read/1803/why-does-helium-make-your-voice-squeaky

and it turns out that i was completely wrong

Edited February 13, 2014 by DonLorenzo

[Deadpangod3]

Ah, ok, thanks!

[Dispatcher]

Proof positive that Kerbin has He in its atmosphere.