system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does it "hurt" when nails are being rubbed against a blackboard?

Is there any instinctive background to that?
gpt
V-Sauce theorized that the human ear is especially good at amplifying sounds around 4,000 hertz, which is the mid range talking voice of a human. When you scratch a chalkboard, it makes a sound in the same range...amplified by your ear makes it seem MUCH louder.