Minecraft: Audio Psychosis.

Picture this: You’re on a world playing both Creative and Peaceful Mode with music turned off and Mob Spawning disabled. You begin to build in peace and quiet, just minding your business when suddenly you hear something similar to a portal. At first, you’re hearing things and continue building. Then you hear it again and turn around to see what it was, but nothing out of the ordinary is there. Is this an audio glitch, in-game hallucination, or is there really something or someone teleporting in your world without you nor even the game itself knowing? I really need answer to this so I can feel better. Please and thanks.