If you listen the quiet room of a library isn't very quiet.
There's the creek of the chairs the rumbling glide of wheeled chairs the tink tap thump of keyboards the rustle swoosh of bag straps sliding off shoulders the clearing of throats and an occasional sigh, the hum of the air conditioner and the buz of florescent lights the tap tap tap of women's shoes and the sudden clink of a dropped pen the slow squeak of the door hinges and the chunk as it falls closed again, pages swish as their turned and someone releases a stack of books as they thump onto the table. a gradual breathing grows louder slower and deeper as someone falls into sleep the quixk zzzzip of a bag startles them back to groggy wakefulness with a sharp saliva filled intake of breath. someone taps their pencil on the table absentmindedly until the sharp through clearing of a nearby neighbor urges them to stop.
Tink-tink tap thump tink-tink thump tap tap tap thump tink thump think tink tap crack swish zzzzip buzz hum ahem.