Measurement and analysis of speech sound radiated from vocal tract wall

This paper deals with the phenomenon that a fairly large amount of speech sound is radiated from the outer surface of vocal organs. It is shown that the quantity of radiation from the wall is not always negligibly small but rather large especially in hyperbaric atmosphere as in the diver\´s speech, and that it is varied depending on the vocal tract configuration. It is also shown that the higher formant peaks in the "wallsound" are almost vanished in the air speech but still remain some extent in the helium speech. Those findings are obtained from a simulation of speech radiation, and evidenced by the experimental measurement of the sounds from lips and others of talkers in several atmospheric pressures from 1ATA to 31ATA of helium-oxygen gas mixture.