system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Voice Cracks

Voice cracks, voice breaks, you name it.
gpt
If you mean why, then it's a one-word answer: tension.

Your vocal cords aren't "cords" at all, they're actually folds. It's a lot like the double reed system you see on instruments like oboes. In order to produce speech, muscles tension and relax the vocal folds as air is blown through them from the lungs. The air causes the folds to vibrate, giving you sound. 

This system is easily upset. If the vocal folds are inflamed (say from yelling a lot or because you're sick), if there's excess mucus in the larynx (where the vocal folds are), or if you're nervous, the ability to properly tension the vocal folds and getting them to vibrate correctly can be impaired. Too much tension or vocal folds that are too inflamed won't vibrate correctly and can stop vibrating altogether as air passes through. When the vocal folds have an interruption of vibration, you get a break. If the muscles spasm and suddenly put the vocal folds under too much tension, you get a crack.