Why does your voice sound higher and funny when you ingest helium?

The kiddie equivalent of the drunken partygoer putting a lamshade on his head is ingesting helium and speaking like a chipmunk with a caffeine problem. Many Imponderables readers want a know to know the answer to this question, so we contacted several chemist and physicists. They replied with unanimity. Perhaps the most complete explanation came from George B Kauffman:

'Sound is the sensation produced by stimulation of the organs of hearing by vibrations transmitted through the air or other mediums. Low-frequencies as correspondingly higher pitch. The frequency (pitch) of sound depends on the density of the medium throungh which the vibrations are transmitted; the less dense the medium, the greater the rate (frequency) of vibration, and hence the higher the pitch of the sound.

The densities of gases are directly proportional to their molecular weights. Because the density of helium is much less then that of air, a mixture of about 78 per cent nitrogen and about 20 per cent oxygen the vocal cords vibrate much faster in helium than in air, and therefore the voice is perceived as having a higher pitch.

The effect is more readily perceived with male voices, which have a lower pitch than female voices. The pitch of the voice can be lowered by inhaling a member of the noble gas family (to which helium belong) that is heavier than air...'

Brian Bigley, a chemist at Systech Environmental Corporation, told Imponderables that helium mixtures are used to treat asthma and other types of respiratory aliments. Patients with breathing problems can process a helium mixture more easily than normal air, and the muscles of the lungs don't have to work as hard as they do to inhale the same volume of oxygen.