Yeah, that was bit odd comment :- ). I would suspect either poor case, CPU cooler, or setup.
Personally, I find CPU tower coolers to be extremely silent, they are for most part massive 140mm fans on heatsink that don't need to spin a lot (<1000 RPM to maintain even high overclock).
My 2x Noctua NH-U14 spin only up to 900 RPM to cool my dual-xeon (2x140W), generating roughly <= 26 dB. It's inaudible almost, I can only hear them when everything else is shut down at night.
Oppositely, if you want to stack a lot of GPUs next to each other, it's preferable to use blower-style reference models, and those generate the most audible noise I am aware of.
This means the Founder's edition of 1080Ti easily reaches 42 dB because it spins up to 4000 RPM. That's jet engine :- )
Only way to avoid it is to use custom water-loop, but you need massive pump to go through multiple GPUs and those pumps spin 2000+ RPM very easily, making it again, rather audible. Such setups are never <30 dB inside massive case.
But of course, scalability is amazing. That's the best feature of GPUs bar none.