24V 3D Printer - power ratings
I see this as a “mechanical” problem often faced by EE’s , that being the ambient noise of high velocity fans with Eddy current acoustic noise on the safety grids.

Techie details

But being EE’s we are much more familiar with Eddy current noise than ME’s.  what you want is a longish laminar plenum tube (square or round) air exit and remove the safety grid wire layer that causes most of the acoustic white noise and whine from propeller/grid frequencies stimulated by the blade pulses going past it.

Construction

It could be a PVC pipe, the diameter of the fan and at least as long as the diameter, the longer the better but not so long as to cause standing wave bass frequencies.

Then you will have a whisper quiet fan at it’s no load ambient noise levels often rated in the -55dBc range.  Mount the fans inside the square wood or round PVC with your ME  on, such that it is mid point of the laminar plenum and voila, your wife will kiss you. (Even more)

FWIW, Dell used inline plenum CPU fans over 20 yrs ago in their very silent forced air cooling towers for under the desk.

I cannot see your fan specs but it is air velocity that cools and not CFM but obviously they are related to load and diameter. You might be able to combine 1 bigger low RPM thick fan to replace 2 thin noisy high RPM fans if that results in the same flow or better air velocity inside.

Even a whisper-quiet fan is a misnomer when it is fastened next to a finger-safety grid.  The Plenum only needs to prevent kids from poking their toys and fingers in it by the distance from the exit to blades and noise depends inversely with impedance mismatch interface gap.