| SPEECH IN AN ARTIFICIAL ATMOSPHERE (44% OXYGEN-56% HELIUM). (2005) | |||||||||
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| Intelligibility and physical characteristics of helium speech were investigated during a simulated space mission at Brooks Air Force Base, Texas. Speech was produced under conditions of room air at ground level, 100% oxygen at 18,000 feet, 56% helium-44% oxygen at 18,000 feet, and 80% helium-20% oxygen at ground level. Results of both objective and subjective analyses of the data show that (1) word intelligibility in the 80% helium condition was less than in room air, (2) when in the presence of noise, intelligibility was less in both 56% and 80% helium mixtures than in room air, (3) the high fundamental pitch observed immediately upon entering the helium atmosphere gradually decreased, but did not return to the prehelium level of pitch, (4) measured rate of speaking was unaffected, and (5) mean second formant frequencies were 1.35 times higher in 56% helium and 1.62 times higher in 80% helium than in room air. Observed ratios were slightly less than ratios predicted on the basis of velocity of sound in the vocal tract. (Author) | |||||||||
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