This is what we need instead of the loud, startling bell that currently warns students that the library will be closing shortly. Or something similar anyway.
As a student (I work at my alma mater), I purposely used to leave the library 20 minutes before closing so as to avoid being scared half out of my mind when that irritating bell rang. The one or two times I stayed too late were enough. I'd be studying furiously and all of a sudden, the bell would sound, and I'd jump half out of my chair. Yech!