Instead of helium, you’ll need sulfur hexafluoride.
Everyone is aware of the ever-so-popular trick of inhaling helium to make your voice go hysterically squeaky and high pitched. But did you know it is possible to do the opposite with another type of gas?
In the video posted below, Mythbuster’s Adam Savage shows what happens when you inhale a gas known as sulfur hexafluoride. It actually works very similarly to helium, except for one major difference.
When you speak, air travels up from your lungs and through the larynx where it meets the vocal cords, which are twin infoldings of mucous membranes stretched horizontally across the larynx. When air hits the underside of the cords, it causes them to vibrate or oscillate back and forth.
This vibration excites air molecules in your vocal tract and sets up resonant frequencies, or in other words, the pitch of your voice. Your voice finally leaves your mouth in the form of sound waves. In short, the harmonics created by your particular vocal folds paired with the shape of your vocal tract is what produces your distinct voice.
There is a common misconception that when you inhale helium it actually changes the pitch of your voice. However, that is not what’s happening.
Here is how it actually works:
Sound travels at 1,128 feet per second (344 meters per second) through air, but it travels 3,041 feet per second (927 meters per second) through helium gas. Since helium is six times less dense than air, the molecules oscillate back and forth much faster than in air (the oscillation is what pushes the sound wave through the gas). This faster movement of sound waves is why your voice sounds higher pitched.
On the other hand, sulfur hexafluoride is six times more dense than air, which means that sound waves travel more slowly through it. This results in a more demonic sounding voice.
Although it is not as funny to listen to as helium, I could definitely think of a few ways to scare my friends with this trick!
Please note, inhaling gases in order to change your voice is not something you should be doing at home. Inhaling too much can lead to a lack of oxygen, which in extreme situations, can be fatal. Also, sulfur hexafluoride is quite expensive.
So as Adam states in the video, don’t try this at home!