The shuffling sounds get louder, but then stop. A very distinctive growling noise takes its place. Something is unhappy with the noises in the library, it seems. And, perhaps, with the theft of the book on washing machine repair, as it becomes rather louder when the Doctor pockets the tome in question.

It's quite possibly not a coincidence that there's a monkey down at the end of the corridor formed by the bookcases, glaring malevolently at Jamie and the Doctor.