Whisperer Trophy in The Bridge

Go back to Chapter I, Stage II: The Library. The goal here is to do the level SLOWLY so you make little to no noise. I recommend going into the options screen and turning off the music so you can hear the sound effects better. The sliding book is the most obvious thing to keep in mind; it makes a loud sound when it switches sides if you don't nudge it along, but things like footsteps count too, so make your way through the stage by shifting around rather than walking.

Solus Sicarius has made a video walkthrough HERE