system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are some radio stations louder than others even when playing the same song?

Is someone checking to make sure they are roughly at the same level as other stations?
gpt
The answer has to do with something called **audio compression**.

Here's a quick ELI5 on Audio Compression:

* You're a teenager watching a movie late at night in your room.

* The loud parts are too loud and you mom keeps hassling you to turn it down. But when you do, you can't hear the dialog. 

* So you buy a strange pet monster from the internet. The monster comes with magic headphones that allow him to listen to the sound from the movie a fraction of a second before it goes to the speakers. 

* You train the monster to turn the audio down just for the brief loud parts and otherwise turn it up so you can hear the dialog. 

* That's audio compression.

The more you compress the loud parts, the more you can raise the level of the whole signal. That makes it appear louder to the listener. 

However, compressing too much will make the audio start to sound weird so you can't do it *too* much.

**TL;DR** *The reason some radio stations are louder is because they compress their audio more than others sacrificing quality.*

**Special Note!** Audio compression is **not the same** as data compression that is used to create MP3s.