PURPOSE: To demonstrate the rise in frequency of vocal formants due to the increase in the speed of sound in a light gas.
DESCRIPTION: Snort a lungfull of helium and talk and sing normally. Your voice takes on a squeaky "Donald Duck" character due to the increase in frequency of your vocal formants.
SUGGESTIONS: Take a couple of big breaths of air first to get plenty of oxygen, then breath out completely before inhaling the helium.
REFERENCES: See Berg and Stork, The Physics of Sound, for a discussion of vocal formants and how this effect works.
EQUIPMENT: Tank of helium with regulator and pressure gauges.
SETUP TIME: None.
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