How does helium change ur voice?

i know that helium changes your voice but how does it do that? what exactly is it doing to me? anyone?How does helium change ur voice?
helium cunducts sound three times faster than ordinary air. As such the sounds made by the vocal chords is higher.How does helium change ur voice?
It changes your voice by making it sound squeakier, at school the other day was our fall festival and a boy in my class did that with a balloon to one of the teachers it was soooo funny!
Helium tightens your vocal cords which leads to a higher pitched sound.