Cave Sounds Origins

The famous cave sounds,that scare minecart tumbling noise etc.

But where do it comes from???

Herobrine,bullcrap.

Demons,even shittier.

The truth is what its Steve is scared or even keyed up,and that is driving he to PTSD-like flashbacks causing him to have this strange sounds,like his past.

Or...

Steve (or Alex) is alone in the world making him go insane, and thus begins hearing these sounds, what dont even have a origin mob or entity to emit these sounds.