system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does our voice sound different when we wake up from sleep?
gpt
your vocal cords are muscles. after sleep all of your muscles are more relaxed. so your vocal chords act like a "floppy" rubber band and produce a deeper sound.

during the day your vocal cords get more tension from talking breathing and gerenal activity so your voice changes slightly over daytime.