system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - Do your ears make adjustments to listen to sounds from different places nearby?

I was listening to a podcast when I started listening to a nearby conversation between people a few feet away from me without adjusting the volume in my earbuds. Every time I switched my focus it’s like the other voices just faded away, how does this work?
gpt
It's not exactly your ears making adjustments, but your brain. 

What exactly those adjustments are is complicated, but it probably involves: 

Beam forming: by adding up the sound coming though your right and left ear with a slight delay, you can boost the signal to noise ratio of sounds coming from a given direction (though with only two ears it'll be a sort of conical donut shape). 

Reverb analysis: your brain has been trained from birth to recognise how the shape of your ear (and the rest of your body for that matter) bounces around sounds coming from different directions and can use this to focus on sounds coming from a specific direction (or more often tell which direction sounds are coming from). 

Frequency analysis: if you're listening to two (average, young) women talking to each other, you can ignore all the frequencies not related to human speech or too low for (most) women to use. 

Pattern recognition: if you're listening to two people speaking a language you know, your brain can use your knowledge of that language to predict what's most likely to be said next given the context of the conversation so far, and pick whatever word fits most closely to the raw sound your ears are reporting.

At least those are the methods used by computers to do the same thing. Except for the reverb thing, that's still really hard to do for computers while the human brain is absolutely fantastic at it.