Buzz
Helium has an atomic number of 2 and an atomic weight of 4.002602. Its boiling point is -452.1°F, and its melting point is -458.0°F, both of which are the lowest among all elements. It ranks as the second most abundant element in the universe, just behind hydrogen. When you inhale helium, it produces a funny sound in your voice. Here’s the explanation.
A Quick Overview of Sound
When you speak, air flows from your lungs through the larynx, where it encounters the vocal cords (or vocal folds), which are two layers of mucous membrane stretched horizontally across the larynx. This contact causes them to vibrate. These vibrations excite air molecules in your vocal tract, setting up resonant frequencies. The pitch (the perceived basic frequency of sound) of your voice is influenced by the vibrations of the cords, while the timbre (the quality of sound that differentiates types of sound production—remember this for later, it’s important) is shaped by the vibration of the air in your vocal tract. By manipulating your vocal tract, such as moving your tongue or lips, you create various resonant frequencies that enable you to produce different sounds like "oohs" and "aahs." Finally, your voice is released as waves—pressure oscillations traveling through a medium.
Voice Meets Helium
In addition to the vibrations and adjustments that shape the sound of your voice, the space in which you speak plays a role in what others hear. The air around us—composed of about 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, and trace amounts of other gases—also affects the sound. Nitrogen, which makes up most of the air, has a mass roughly seven times greater than helium. As helium is lighter than air, sound waves travel through it at a higher speed. In a room at 68 degrees Fahrenheit, sound travels at 344 meters per second through air, but at 927 meters per second through helium. When you inhale helium, you alter the gas in your vocal tract, speeding up the sound of your voice.
Many believe helium raises the pitch of the voice, but in reality, the vibration frequency of the vocal cords doesn't change with the type of gas surrounding them. When you breathe in helium, your vocal cords continue to vibrate at the same rate. What actually changes is the timbre (the unique quality of a sound that distinguishes different types of production, also called tone quality or tone color). The lighter helium molecules allow sound to move faster, modifying the resonances of your vocal tract, making it more sensitive to high-frequency sounds while dampening lower ones. The result is a voice that sounds higher-pitched, like a cartoon character, which listeners interpret as a pitch shift.
More Fun With Gases
If inhaling a lighter gas like helium makes our voice squeaky, you might guess that a heavier-than-air gas would lower the resonant frequencies and make the voice deeper and more resonant (imagine swapping Donald Duck for Barry White). And you'd be right! Gases such as xenon and sulfur hexafluoride slow down sound waves and lower the resonant frequencies of your vocal tract.
No Fun With Helium
As entertaining as the effects may be, inhaling helium isn’t as harmless as it seems. While you're inhaling it, you're depriving your body of the oxygen needed for proper respiration. Prolonged inhalation of helium can lead to suffocation within minutes. That light-headed feeling after a few breaths is a warning that you need to stop. And never, under any circumstances, inhale helium directly from a pressurized tank. The rapid airflow can damage your lung tissue or force a large amount of gas into your bloodstream, potentially causing it to travel to the brain, leading to stroke, seizures, and even death.
This article was first published in 2009.
