From The Philosophical Magazine 4: 9 (1799): The effect of hydrogen gas on the voice:
“The Journal Britannique, published at Geneva by Prevot, contains the following article :– “Maunier was one day amusing himself with Paul at Geneva, in breathing pure hydrogen air. He inspired it with ease; and did not perceive that it had any sensible effect on him, either in entering his lungs, or passing out. But after he had taken in a very large dose, he was desirous of speaking, and was astonishingly surprised at the sound of his voice, which was become soft, shrill, and even squeaking, so as to alarm him. Paul made the same experiment himself, and the same effect was produced. I do not know whether any thing similar has occurred in breathing any of the other gases.”
I bet after they got over being ‘astonishingly surprised’ they laughed themselves silly! But wow that dense gas the Mythbusters dude inhales in the second half could be VERY useful for demonic/creature ADR! We’ve achieved a simialr result in real time using a Sennheiser 80X0 mic that goes up to 50k, sending it through the PT TDM Pitch plug dropping it an octave or so & then sending that back to the headphones of the performer, so the sound affects their performance – works very very well!
Hmmm where to buy sulfur hexafluoride?