sound measurement is absolute, however perception of sound is subjective.
tonality and harmonics can make sounds seem "louder" or "quieter" to the ear, however it's not so much to the instruments measuring the sound. a perfect example would be something like coil whine. on an instrument, it may not register a very high dB level. however to the ear that happens to be attuned to the frequency of the whine, it's the loudest noise you can hear
so, the arguments here is somewhat none productive since it really all depends on the conditions and the tone of the noise. a long time ago, i didn't think the noise of HDD platters spinning bothered me as much as the drive heads slashing across the platters. however i've gotten so used to SSD these days, the spinning platter noise actually cause me more of a stress then the drive heads moving around the drive. another issues is the ambient noise where the system is placed. a 23db GPU may seem absolutely silent in an environment where the ambient noise level is 32db. but in the bedroom at the dead of night where ambient noise is around 15 db, that same 23db GPU may be loud enough to keep you awake.
the bottom line is each of us have our own comfort level as to what we consider "quiet" my personal threshold is the sound of a central AC unit. if the system is quieter then the central AC unit when the air conditioner is on, then it's considered "quiet" my logic is if i can fall asleep while the air conditioner is running, then any noise level below that is "acceptable". obviously the noise level of each air conditioner is different and depending on where it's located and what room you are in, the noise level can vary greatly, however like i said, it's MY threshold for my house. all i can say is it's quieter then the crickets outside my house at night
i know people who are perfectly comfortable with the noise level of a fan going at 1200 RPM, personally i prefer the noise level of a fan at around 700RPM or less. it's all subjective so we can argue all day and night and will never come to a consensus on what is considered "quiet" or "silent"