Yep. Those things in your throat that open and close to allow you to speak have an interesting commonality with airplanes. It’s all about the airflow. (*side note: vocal folds and vocal cords are the same thing—they are referred to as vocal folds by SLPs and vocal cords by medical professionals)
Bernoulli’s Effect states that an increase in the velocity of a stream of fluid results in a decrease in pressure. When an airplane picks up speed there is an increase in airflow across the wings. As the velocity increases more, the pressure below the wings become greater than the pressure from above, allowing lift to occur. There is an inverse relationship here between pressure and velocity.
Basically the same thing happens in your throat (which is weird to think about, but true nonetheless). The glottis is the space between your vocal folds. When air pressure from your lungs flows up through this narrow passageway when you exhale, the result is an increase in velocity. Then just like in the airplane example, a drop in air pressure occurs. This causes the vocal folds to be sucked together. The vocal folds are also aided in this re-closure by their elastic properties. They act kind of like rubber bands, when pulled tight there is an increased closure (less space between them).
The faster your vocal folds vibrate by opening and closing, the higher the pitch of your speech. Similarly the slower the vibration, the lower the pitch.
All the sounds in the English language are egressive sounds, produced with an outward flow of air from the lungs during exhalation. Some other languages produce some sounds while inhaling, called ingressive sounds.
Now back to studying for the two midterms I have on Monday! I hope everyone is having a great semester so far!