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Question: Is it dangerous to swallow helium and how does it make your voice sound different?
These are great questions. Why do you sound like a chipmunk when you breathe helium?? It's because of how sound moves through helium. Helium is the second-lightest element after hydrogen, and helium gas is almost 7 times less dense than air. This means that sound travels through helium almost three times faster than through air.
We speak by pushing air from our lungs past the vocal cords in our throat. The vocal cords are two flaps of tissue that vibrate under the pressure of the air from our lungs. This vibration causes sound waves to form. The shape of your larynx, mouth, tongue, and lips determines the frequency, or pitch, of this vibration. The smallest frequency of sound wave produced is called the fundamental frequency. Other frequencies that occur in a sound wave are called resonances, and are multiples of the fundamental frequency.
A common myth is that helium increases the pitch of your voice. When you breathe helium, your vocal cords still vibrate at the *same* frequency, so the pitch is the same. But because sound travels faster through helium, the higher resonances become more powerful and the lower resonances have less power. The pitch does not change, but the timbre of your voice does. That's why your voice sounds much higher!
By the way, the same theory works in reverse. If you breathe in a gas, which is heavier than air so that the speed of sound is slower than in air, your voice will sound very deep. Breathing in Sulfur Hexafluoride, for example, will make your voice sound deeper than Barry White's!
But is helium dangerous to breathe?? Helium is fairly safe to inhale, but it can be dangerous if you aren't smart about it. Don't inhale too much, and don't breathe it from a canister.
Helium itself does not cause a harmful chemical reaction in your body. It's a noble gas, so it is chemically inert. It makes up a small part of normal air. And deep-sea divers regularly breathe helium, mixed with oxygen and nitrogen.
Rather, the biggest danger from helium is taking in too much. We all need oxygen to live, and if you breathe in pure helium then you aren't breathing in oxygen. If your body doesn't have enough oxygen, you could suffocate or deprive your brain of oxygen (this is called asphyxiation). If you've breathed helium before, you may remember feeling a little light-headed from it. That's because of the lack of oxygen in your blood. If you feel light-headed, stop breathing helium!
One more word of caution: never inhale pressurized helium (or anything else!) directly from a canister or tank, like those used to inflate balloons. This causes the helium to be forced into your lungs or blood stream. It can severely damage your lungs, or worse yet, cause a deadly helium bubble in your blood.
Breathing helium is a perfect example of a scientific experiment: have fun, but be careful!
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