The Observer would not be able to detect via noise, instead it would have to be able to directly see the player, upon first sight the players screen will turn red and lock onto the Nextbot then the Observer will B-Line towards them for a jumpscare, if the player is in a higher area it will fly up.

If a player stares at The Observer too long even from an obscured region their screen will slowly shift to a red tone, if they allow the full shift then the Observer will detect them.

Appearance: Maybe some type of eye monster