Isn’t it funny to hear someone who has just gulped a bit of helium from a balloon speak with a squaky voice? Clowns and comedians use this trick to make audiences laugh in parties. People may think it’s a joke, but why does helium change one’s voice? It’s nice to know why it happens.
Warning! Helium is not safe!
First of all, let’s give out a warning about helium. Helium is a dangerous gas to play with. Breathing in pure helium deprives the body of oxygen, as if you were holding your breath. This cuts off the oxygen supply to your brain and causes a person to collapse, and perhaps suffer brain damage after that.
What’s worse is that helium speeds up the process of sucking oxygen out of your system. When the gas fills your lungs, it creates a diffusion gradient that washes out the oxygen. In other words, each breath of helium you take sucks more oxygen out of your system. After inhaling helium, the body’s oxygen level can plummet to a hazardous level in a matter of seconds.
Breaking the myths
Now that we have properly warned you of the dangers of helium, let’s proceed to breaking the misconceptions about helium speech. People think that helium affects how fast or how small the vocal tract contracts and expands when exposed to helium. But contracting the vocal slit to as small as possible only produces a whispering voice, and not a squeaky voice. Besides that the squeakiness of a helium voice does not actually differ in pitch from the natural voice.
Another myth of helium speech is that the helium being expelled when we speak makes the sound of our voice travel faster. However, if our vocal folds vibrate at a particular frequency, say 100 times a second, there will still be 100 pulses a second reaching the other person’s ear, no matter how fast or through what changes of medium they travel.
So what really changes in our voice?
Since we have established that helium neither changes the pitch of one’s voice, nor hastens the speed of the sound of your voice through air, then the reason for the squeaky helium voice is found somewhere else.
Based on research, the reason for the squeakiness is in the resonance of the sound inside the vocal tract. Since helium is lighter than air, sound travels faster in it. Inhaling that bit of helium has filled your vocal tract with it, and any sound created within will travel much faster than when the tract is filled with ordinary air.
The helium increases the frequency of the sound waves, and when you speak the sound comes out faster. The same effect is heard from a record that has been forwarded faster than normal. Since each element of speech is composed of a pattern of several frequencies, altering the speed of sound distorts that pattern.
To generalize, we find that helium does not affect your vocal cords, and helium drastically changes the timbre of your voice without having any significant effect on its pitch. It happens that helium is less dense than air, and so, the speed of sound is much higher in helium.
Further Readings: