I suggest that you stop using the bell to kick people out of the library. It's very annoying (though that may be the purpose of using it). Why not try to use a more "civilized way" like what they use in the department store? Open a record that tells the library users more politely.
PS. You should try listening to that bell, it's noise pollution!
We presume you are referring to the Regenstein closing bell. The closing bell at Crerar is a soft chime that we speculate you would consider quite "civilized."
The JRL bell is intentionally loud, to awaken slumbering students and encourage them to leave the Library. We are afraid that a softer bell would mean encountering students coming down the main stairs at 2 AM, yawning and explaining they "slept through the bell." We already encounter this situation occasionally, and while our night entry control staff usually cock a skeptical eyebrow at the person employing this excuse, we usually give students the benefit of the doubt and let them go home.
We admit that a loud bell may not be as necessary during the summer, especially when the Reg closes at 5 PM. However, seasonally changing all the bells -- the volume isn't centrally controlled, as far as we know -- would be a time-consuming and expensive process.
Unfortunately the Reg does not have a public address system, so we can't make a voice announcement about closing. (One member of the staff fondly recalls his hometown public library, which did have a PA system. The staff would announce closing time, then play music as patrons left.) So it's the bell or nothing at all -- and our experience overwhelmingly demonstrates that U of C students need some encouragement to leave the Library.
[A side note: louder than the closing bell, and quite distinct from it, is the fire alarm. Suggestions Office staff sometimes observe -- in passing, as we flee towards the exit -- some students defiantly ignoring the alarm and continuing to study. We understand the desire to prove one's dedication to the text at hand, but PLEASE vacate the building when the alarm goes off. Even when it's a false alarm, the Chicago Fire Department gets very upset with us when they find people inside the building.]