Today’s Wonder of the Day was inspired by Mary from AL. Mary Wonders, “how do our vocal cords work?” Thanks for WONDERing with us, Mary!

If you're like many children, you've probably seen — and heard! — someone inhale helium from a balloon and then speak in a funny voice. Some people who do this sound like a duck, while others might sound like a squeaky mouse. What's going on here?

The sound of your normal voice is determined by a number of factors. In addition to the air you breathe, the shape of your mouth, throat, nasal passages, tongue, and lips all contribute to creating the unique sound that is your voice.

Your voice begins in your voice box, which scientists call the larynx. Your larynx contains your vocal cords. These two folded mucous membranes vibrate when air passes between them. These vibrations resonate throughout your throat, nasal passages, mouth, tongue, and lips to create the sounds you make when you speak.

The air you breathe is made up mainly of nitrogen and oxygen. Helium is much less dense than regular air. That's why helium is used in balloons to make them float.

Due to its lower density, sound travels over twice as fast through helium than it does regular air. When you breathe in helium, your voice travels much more quickly across your vocal cords. This results in the funny sounds you make when you talk after breathing helium.

Some people think that the helium changes the pitch of your voice. In reality, however, your vocal cords vibrate at the same frequency. The helium actually affects the sound quality of your voice (its tone or timbre) by allowing sound to travel faster and thus change the resonances of your vocal tract by making it more responsive to high-frequency sounds.

Helium is the second most abundant element in the known universe (hydrogen is the most abundant). Inhaling a couple of breaths of helium is usually harmless. Breathing a lot of helium, however, can be dangerous.

Prolonged inhalation of helium can lead to an inadequate amount of oxygen in the lungs and blood. This, in turn, can lead to brain injury and, in rare cases, even death. A few puffs of helium from a balloon usually isn't a big deal, though.

In fact, helium can be helpful in some instances. Doctors have sometimes treated chronic obstructive pulmonary disease (COPD) with a mixture of helium and oxygen. Helium's lower density can help improve airflow in the lungs of people with COPD.

If you've ever breathed helium and heard the sound of your voice, you've probably noticed that the effect wears off quickly. That's because the effect only lasts as long as there's helium around your vocal cords. As soon as regular air replaces the helium, your voice returns to normal.

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