Why Helium Makes Your Voice High Pitched (And Makes You Feel Lightheaded)

Helium is the second-most abundant element in the entire universe, and the gas has numerous everyday uses in human industry. However, most of us know helium for just two things: It makes party balloons float, and if you inhale it, you'll sound goofy as all get-out. There's a bit of interesting science behind this ever-popular party trick, but first, we need a quick crash course on how your voice works in the first place.

The sound of your voice is produced by the vibrations of your vocal cords, a pair of muscles that stretch across your larynx (aka voice box) at the top of your throat. When your vocal cords are closed, they trap air inside your larynx, but as you move your mouth to speak, air slips between the cords, causing them to vibrate at varying resonant frequencies, which together produce the full range of human sound.

The air we typically breathe is mostly nitrogen and oxygen, both of which are considerably heavier than helium. That's why a balloon filled with helium rises higher than a balloon filled with oxygen or with plain air. Because helium is lighter than air, sound waves travel through it faster. This changes the resonance of your voice, amplifying high-frequency sounds and suppressing low-frequency sounds. It doesn't actually change the pitch of your voice, as your vocal cords still vibrate at the same frequency, but it creates the illusion of a pitch change by changing the timbre of your voice.

If you mess around with the voice-altering power of helium for too long, you'll eventually find yourself getting light headed. This points to the serious side of breathing helium, a side that is anything but fun and games. When you inhale from a helium-filled balloon, the helium entering your lungs forces oxygen out. Repeatedly inhaling helium is no different from suffocating yourself, which is why you quickly start to feel lightheaded, just as if you were holding your breath for too long.

Excessively inhaling helium can cause hypoxia, which is when the body's tissue cells do not get enough oxygen. Hypoxia can lead to organ failure, and poses a particular threat to the heart and brain. There is even a risk of death by asphyxiation from overconsumption of helium. Although most adults can safely take one breath from a balloon for a laugh, even small amounts of helium can pose a risk to young children and people with medical conditions, so it's best for them to play it safe and avoid inhaling helium altogether.