It would be appreciated if the mechanical noise in the Mansueto library were quietened - it does pretty hard to concentrate. It's unfortunate that this beautiful building's usefulness is diminished so. Two librarians have told me that the noise (one said it was the air conditioner) is ever present.
The space underneath the dome in Mansueto is essentially one giant room, and consequently the heating or air conditioning runs pretty much continuously to keep the space at a comfortable temperature.
While we might wish the system were a little quieter, the long-term "residents" of Mansueto tell us that (in time) they stop noticing the noise -- and that the background "white noise" helps mask other sounds such as the noise of book retrievals.