system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do artists performing on stage need in-ear pieces?

I've heard that in-ear pieces help the artist hear themselves better, but why is it necessary? Audience members can hear the artist fine, so what changes on stage?
gpt
Speakers are typically pointed towards the audience, not the performer/artist. If you point speakers at the performer, they’ll play into their mic, the sound will come out of the speaker, the sound coming out of the speaker will play through the mic, *that* reproduced sound will playback through the speaker, which the mic will...you get it. An endless loop results, this is called feedback. That squeaky riiiiiiiiiingiiiiiiiing sound you hear when Bobby stands nervously on the stage for his spelling bee, is feedback and should always be avoided. You can direct all your speakers away from the performers, however the performers need to hear themselves too. So, in order to reduce feedback you can use monitors, which are smaller speakers that direct sound close to the ground (away from the mics on the stage) or you can play the mix back to the performers through ear pieces.

Even if feedback wasn’t an issue, another reason to use ear-pieces is that sound is awfully fickle. Sound bounces off walls, is absorbed by materials (and people) and can be reflected in all sorts of crazy ways. Playing back the  “pure” feed to the artist helps them gauge their performance as they perform and ensures that what they’re hearing is what their audience is hearing.

One last reason a sound engineer may want to use ear-pieces is that they can control what the audience hears versus what the artist hears. If you have a multi-person band, the drummer and guitarist may have different preferences on what they need to hear. A sound engineer can playback a mix that is specific to each member of the band so the members can better coordinate timing and tempo with each other.