system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 Why do bottles make the “whooooo” sound when you blow on the tops of them?
gpt
As your breath flows over the open mouth of the bottle, it sucks some air along with it, out of the bottle. You might think, cool, so the pressure in the bottle drops a little bit, how does that make a noise?

Well, the flow of air out of the bottle builds up some momentum, and it keeps flowing out, even after the pressure in the bottle reaches drops low enough to balance the air-getting-sucked-out effect. So, after a brief moment, air starts getting sucked back in. But this air movement has momentum, too, so the pressure overshoots in the other direction.

This cycle happens continuously, maybe a couple hundred times per second— it depends on the bottle— and, well, changes in pressure that cycle back and forth anywhere between about 50 and 2000 times a second is basically what sound *is.*