Helium Speech
K. Holywell, G. Harvey · The Journal of the Acoustical Society of America · 1964
“Helium Speech” is a term used to describe speech produced whenever an appreciable proportion of helium is present in the vocal tract. Some measurements of the formant frequencies of helium speech are given, and two simple methods for increasing the intelligibility of this speech are described. The results achieved in some preliminary tests of these processing techniques are given.