The Noble Gas Voice
Perhaps the most ubiquitous chemistry trick is helium in a party balloon. Suck in the gas, get a funny voice. Many people have tried it, most people have witnessed it.
Here is unparalleled acting genius Vin Deisel demonstrating the effect of helium on a human voice:
Why does helium have this effect on the voice? One popular notion is the gas changes the pitch of the vocal emanations. Not so! The pitch of your voice is determined by the frequency of the vibrations produced by vocal cords in your larynx. Helium does not alter the frequency our flaps emit.
Instead, helium changes the timbre of our voices. Timbre is the reason a note played on different instruments sounds differently. Despite producing a different tone, a guitar and a piano playing the same note will actually create waves of the same frequency. It can be a bit confusing, so I recommend watching the next video to better understand timbre. Essentially, when instruments (including human voices) make sounds, we produce more than one wave at a time. The shape of an instrument or a throat and mouth has drastic effects on the tone produced. Our voices sound unique thanks to the singular topography of our anatomy.
How does helium mess with the timbre of a voice? Physics (and chemistry)!
The air we breathe is composed mainly of oxygen and nitrogen. A sound wave is a movement through physical matter, so part of our natural timbre is dictated by the air we breathe. When someone inhales helium, they are changing a big part of that timbre machine inside the mouth and throat. Helium is far less dense than regular air, which allows sound to move more quickly through it. Because the waves move faster, the entire sound equation changes. In the case of helium, the higher pitches are amplified. The result is the sound of a duck or a singing chipmunk, despite your vocal cords producing the same frequency waves!
The effect can move in the other direction, too. Sulfur hexafluoride is a gas that is denser than normal air. When you inhale it, the sound moves more slowly and the voice sounds lower!
Theoretically, any gaseous element or compound could be used to alter the tone of your voice. Helium and sulfur hexafluoride are relatively safe to employ because they are inert. Just because they won’t cause any tissue damage, however, does not mean one can be completely mindless when creating party tricks. Breathing too much helium means you are not breathing oxygen, which means you cannot continue to live. The same can be said for sulfur hexafluoride, though its density poses another risk. Because it is heavier than normal air, it can sink to the bottom of your lungs. Too much SF6 and you might need to literally do a handstand to expel it from your lungs!
Non-inert elements can be a big problem. Inhaling chlorine will ravage the lungs and might do you in on the spot. It makes sense that helium is a safe medium for altering a voice since it is one of the Noble Gases. These elements were originally known as inert gases. Making up the last column of the periodic table, noble gases are, at standard conditions, all colorless, odorless, monatomic, and chemically non-reactive.
In addition to helium, we got five other naturally occurring noble gases: neon, argon, krypton, xenon, and radon.
We know that helium makes duck sounds and we’ve now seen that sulfur hexafluoride veers toward Darth Vader. What would happen with the other inert gases?
Since we discovered the effect of gas on the voice stems from the density of the gas, it’s no surprise that the lighter nobles generate higher sounds and the heavier ones deliver lower tones.
Helium – Donald Duck
Neon – Gilbert Gottfried
Argon – Walter Cronkite
Krypton – The voice a character hears in a film when the character is drugged or passing out
Xenon – James Earl Jones doing Darth Vader through a voice alteration machine
Radon, in addition to being radioactive, is extremely difficult to obtain, so it wasn’t tested. Interestingly, xenon has anesthetic properties and has been used medically at times for that purpose. The above video demonstrates the density of heavy gases and the numbing ability of the gas.
We should probably stick to helium and sulfur hexafluoride!