Helium changes the ‘timbre’ of your voice (timbre is the quality that makes the same note on a different instrument sound different – like the same note played on a piano or a violin).
Sound waves can travel much faster through helium than air so as the sound waves are produced by the helium passing through your vocal folds the fast waves in the sound (high pitches) are amplified when the bounce around the vocal tract and the slower waves in the sound (low pitches – like when you listen to someone through a wall) are lost.
Comments
Tim commented on :
Thanks Suzi – yep I tried it once and I agree it is very silly, but fun!