Here's the fan in my NetGear GSM7328Sv2:please show the fan with the same CFM but much less fan noise
you can not beat space constraint on 1u. you would replace with lower CFM and RPM.
on my knowledge replacing low RPM and CFM on 1U is useless due on space constraint.
Here's an equivalent fan that's quieter (maybe not "much less" according to your standards though):
Amazon.com: Sunon 40x40x20mm 3 pin fan #KDE1204PKVX: Computers & Accessories
Here's a fan that's probably close enough with decent airflow that's logarithmically almost half as loud:
Also take into consideration the specifications of the chassis and it's temperature ratings. If your equipment is in a basement like mine and it doesn't ever get above 60 degrees, you have some wiggle room to play with and can lower your CFM while still maintaining a safe temperature range.