PURPOSE: To demonstrate the drop in frequency of vocal formants due to the decrease in the speed of sound in a heavy gas.
DESCRIPTION: Snort a lungfull of sulfur hexafluoride and talk and sing normally. Your voice takes on a deep, muffled character due to the decrease in frequency of your vocal formants. This is a REAL HOOT, and should be done with the helium voice whenever the appropriate occasion arises.
SUGGESTIONS: Take a couple of big breaths of air first to get plenty of oxygen, then breath out completely before inhaling the sulfur hexafluoride.
REFERENCES: (PIRA 3B30.50) See Berg and Stork, The Physics of Sound, for a discussion of vocal formants and how this effect works.
EQUIPMENT: Tank of sulfur hexafluoride with regulator and pressure gauges.
SETUP TIME: None.
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