To perceive sounds with your ears
Encoding Strategies:
mnemonic

oh, ear!
reacting to a sound
Oír means to hear and sounds like "oh, ear!0" — like saying "oh!" when a sound reaches your ear.
oír
to hear
To perceive a sound with your ears, whether or not you were trying to.
Las paredes son tan finas que oigo a los vecinosThe walls are so thin that I can hear the neighbors
¿Oyes ese ruido?Do you hear that noise?
to hear (news / information)
Just like English "Did you hear?", oír also covers finding something out.
Oí la noticia en la radioI heard the news on the radio
¿Has oído lo que pasó ayer?Have you heard what happened yesterday?
oye / oiga
hey, listen (to get attention)
Literally a command to "hear": you tell someone to lend you their ear to get their attention. Oye is informal, oiga is formal.
Oye, se te cayó la carteraHey, you dropped your wallet
Oiga, ¿me puede ayudar?Excuse me, can you help me?
oírse
to be heard, to sound
When something "hears itself," it can be heard, or it sounds a certain way.
No se oía nada por el ruido del aviónNothing could be heard over the noise of the airplane
Tu voz se oye muy lejanaYour voice sounds very far away