H6-04: HELIUM VOICE

ID Code: H6-04
Purpose: 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.

This demonstration can be dangerous, and must only be used after instruction by Lecture-Demonstration personnel. The purpose of this demonstration is to illustrate the effect of vocal formants, not as entertainment for groups where the physics content is not discussed. Take a couple of big breaths of air first to get plenty of oxygen, then breath out completely before inhaling the helium.

Availability: Available

Interestingly, in his The Sound Book, Trevor Cox notes that this does not work on frogs - resonance in the vocal sac is not the source of amplification for their voices.

Further details: umaryland.on.worldcat.org/oclc/5553761940?databaseList=638 Rand & Dudley, "Frogs in Helium: The Anuran Vocal Sac Is Not a Cavity Resonator," Physiological Zoology v66 n5