every sound is the monster moving closer, monsters move closer incrementally if you didnt notice that they dont instantly come after everything. some sounds are due to the gimmicks, like a monster taking a battery. flashing every time you hear something wastes your time to do the tasks. dont criticize a sit and survive horror game for being a sit and survive horror game then give a bad review bc you suck at it.
Real, the sound is intentionally unreliable in this game to make you paranoid and it's great. That's why you're meant to use the decibel meter (which the game explains clearly how it works at the start). By using this, you can reliably detect monster movement. The higher the bar gets on the meter, the closer the monster is. The reason you kept flashing and nothing was there is probably because you kept flashing when the meter was low (monster far away).
So overall it just seems like you don't understand the game, you're bad at the game, and you should probably go play something else because this clearly doesn't seem to be your type of game.