the sounds also amused him : the rippling sound that signified the turning of a page or the unrolling of a scroll ; the squeak of the chair as a reader shifted weight ; the louder scrape of a chair being vacated and replaced beneath a table ; the rattle of the ladders as they moved down their wheeled tracks ; andunderneath all of thosethe barely perceptible hiss of whispered voices , as though the humans moving among the ancient tomes recognized that silence and reverence were due .