system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What changes are made to a male's vocal cords during puberty ?
gpt
The larynx expands outward (back to front), which lengthens the vocal cords and expands the volume of space where the voice can resonate.

The sinuses also expand as a person's skull grows (and there are changes in the shape of skulls of both men and women as well that come with hormones), which also expands the hollow spaces where a person's voice resonates.

Longer cords + more space for resonance = deeper voice.