heliummmm

[b.dubbb]

when people inhale helium gas, why does the pitch of their voice change?

[ermadea]

http://www.bbc.co.uk/dna/h2g2/A865929
http://www.howstuffworks.com/ddhelium.htm

[jake-the-peg]

You get exactly the same effect in a decompression chamber for the same reason.

Sound travels faster in high pressure air just as it does in normal pressure Helium. The result is that if you are in a decompression chamber and the pressure increased to 2 or 3 times its normal value you're voice goes all squeaky too.

[mibn2cweus]

Helium gas has a lower density than regular air. This reduces the virtual depth of the resonant cavity between your vocal chords and your mouth. The result simulates what would happen if your vocal chords were moved up from your throat to a position somewhere within your mouth.
A similar effect is produced when you alter the resonant characteristics of your voice by changing from the Oooo sound to the Eeee sound without changing the pitch of your voice.
The fundamental pitch of the sound remains the same. It is the reduction of resonant reinforcement of the lower harmonics that contribute to the apparent change in pitch.

[jake-the-peg]

How does that explain the decompression chamber effect mibncweus? where the density is higher due to the increased pressure?

[mibn2cweus]

This is an example where two completely different mechanisms can produce similar results. Although the resultant effect is nearly identical it is for different reasons.

With helium the virtual dimensions of the cavity are reduced proportionately with the change in the density of the medium (pressure remaining the same) of sound propagation

Changing the density of a given medium (air) through pressurization does not greatly alter the speed of sound propagation as the two (pressure/density) have inverse effects on the velocity of sound.

My guess is that the denser pressurized air has an effect on the mechanics of the vocal chord to air interface; perhaps increased resistance is producing the change in the timber of the voice?

But then now as always I could be wrong ~ <�?

[mibn2cweus]

. . . oh yeah, by the way, if you could manage it I'd be curious to learn what would happen if you took a balloon of helium in with you next time around?

[jake-the-peg]

I've only done it once, it's hillariously funny as the high pressure Nitrogen gives you "narks" a bit like being slightly drunk - add that to the squeaky vioce and it's pretty funny.

Of course a baloon of helium would be pretty small and difficult to breathe from at 6 bar so you'd have to pipe in helium - not a trivial experiment.

I guess then a tape recording played in a helium or pressurised atmosphere would sound the same - unfortunately I don't have a chamber to hand :c(

[mibn2cweus]

Jackpot! found these links:

The Helium "Donald Duck" Effect

Speech Distortions in a Hyperbaric Chamber

jake-the-peg, A tape recording, excellent idea. Imagine playing that back at double speed!