system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If you and a sound travelled at the same speed, what would you hear?
gpt
**TL;DR**: *You won't hear it because you're perfectly riding its pressure wave, just like a perfectly timed motorboat can ride ocean swells without going up and down.*

A soundwave is a difference in pressure that moves through the air at a certain speed. You "hear" it when the difference in pressure contacts your eardrum and your brain interprets it as a sound.

Say you're standing still and someone nearby cracks a whip. That whipcrack creates a very sharp "bump" in pressure that launches outward in a wave. That wave passes over you and contacts your eardrum, and KERACKK.

Now say you're travelling away from the whipcrack at the exact same speed that its pressure wave does. What's going to happen is that you're "Stuck" in the exact same pressure since you're in the middle of that soundwave, effectively riding it just like a motorboat can ride the top of a wave on a windy ocean. In the same way the motorboat can stay exactly level, even in giant waves, as long as it's speed is exactly right, your eardrum will stay still because the pressure it's experiencing is not changing.

You'll still hear other sounds coming at your from other directions, assuming your ears are protected from the MASSIVE amount of air that's flowing over them at super-high speed. But you won't hear that whipcrack.