Morgan Freeman, host of Through the Wormhole on the Science Channel, has a characteristic baritone voice. What is better than listening him describe the most difficult concepts about the Universe in a voice that is smoother than silk? Hearing him do it on helium.Why does inhaling helium make voices sound funny?
The density of helium is lower than nitrogen, so when an individual who has inhaled helium starts to speak, the gas disturbs the wavelength of the sound waves coming out, letting them to travel more rapidly. Thus, the result of inhaling helium is a short-term squeaky voice, suggestive of Alvin and the Chipmunks.