What is static pressure? What does it mean for the fan, and why is higher pressure more quiet?
When fans face back pressure (static pressure), different fans respond differently.
Some fans that "have high static pressure" handle the back pressure easily and continue to move CFMs of air.
Other fans handle the back pressure poorly. Instead of moving air the flan blades luff and stall. Generally this increases the noise of the fan. Such fans are said to "have low static pressure".
All things equal (which they never are) you would expect a "high static pressure" fan to operate more quietly against high back pressure (and also deliver more CFM while doing so)... and you would expect a "low static pressure" fan to be able to deliver more CFM under low back pressure... and do to so more quietly than a "high static pressure" fan.
Noiseblockers have a reputation for being quiet at all pressures and for handling high back pressure just fine.
If the fans are making noise, you need to experiment with different fans. Nexus is a good choice. So are Noctua fans if you operate them at low voltage. It may be you just got a bad sample of noiseblockers.
All you can do is experiment.