I made a velocity stack for a 40mm fan.
It may or may not silence the fan, and it may or may not increase fan performance,
but it certainly looks like air is going in there like a maniac.
I made the cone hollow, to save some plastic :-)
set it at 15, but it doesnt matter
Use your own settings, but be warned:
bump up the quality too much and it might just generate cyclones haha