system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the key of a song playing on a set earphones change when the earphones are at some distance from the ears?

I was listening to a playlist on my earphones and after a while I dropped them not too far from my ears. I could still hear them but it sounded like the key had changed. Same thing happened when I put them back on, key returned to normal. Whats the cause of this?
gpt
Higher frequencies get dampened harder over the same distance.  
Additionally, you can only hear sound thats at least a certain loudness.  
Headphones are low-power speakers and if you increase the distance high frequencies seem do drop out because the fall under that threshold.  
The last thing to disappear if you increase distance is bass.