system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: How are we able to “hear” sounds or even songs in our head even though they’re not actually there?
gpt
When you truly hear the word "house", you don't actually hear it at "when it comes to your ear". There's a sound wave that gets interpreted by your ear and then your ear send the instruction to your brain to interpret that sound wave as the sound "house". Of course the speed which all of this occurs is very fast to perceive so it pretty much appear as instantaneous for us.

So in a way, all sounds (the way we hear) are in our head waiting for some external stimuli to tell which combination of sounds we should hear. Our ear send the information to interpret those sounds, the place they're coming from, the volume, etc... 

Think of it as a piano. In a way, every chord is there and all possible sounds are there waiting for someone to press something. It's pretty much the same with our brain. We have within ourselves every possible thing we can hear waiting for some stimuli to trigger it.

Thing is other factors can activate those neurons that codify sounds, like thinking about a music. Of course, not in the same intensity as actually hearing a sound does.