system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come one headphone sounds loud, but together they do not?
gpt
Brain automatically puts more focus on one ear if a distinct sound (music, speech, whatever) is being fed specifically into that ear. That could give the illusion of it being louder, even though it isn't.

It's somewhat relatable (very vaguely :P) to when people close one eye while aiming a gun, i.e. narrowing down their visibility to focus better.