Thanks, indeed the Noctua fans are worth the additional cost and actually not really expensive. (Assume you also added a voltage step down module for your fan)
Indeed, the bearings on these kind of fans often wear out at some point, increasing noise. lubricating (remove label for access to bearing) or replacing the fan reduce noise caused by a worn bearing. Rubber fan mounts help reduce vibration noise further, even with new fans. If the new bearings work silently enough for you printer model a better mount may not be necessary.
My Wanhao Duplicator 4S also has that fan, and it makes a lot of noise, but the problem is not vibration, it's the bearings, or some crap got inside... I'll have to get it replaced soon. I think when I do I'm also going to replace the ones for the hotends, I guess Wanhao used cheap fans, the one I added for the part cooling is still fine, so I'll get more of those.
I notice your Dreamer is the older version....mine is the clear door version, and my driver fan is far thicker at 25mm. It's only a slight humming sound and can't be heard once starts printing. I am more concerned with the rear fans...very noisy and not PWM controlled. I find it unnecessary to spin at full speed. The existing fan is 9-bladed and 15mm thick. Short of adding a manual control, I wonder what are the variables to reduce the noise - 11-blades, 7-blades, 10mm thick, 25mm thick? Thinking of it, perhaps a thicker fan is less noisy, if I compare to my thick driver fan.
Good to see they have improved the driver board fan in the newer versions. My rear fans are quite loud as well, might be good to look for alternatives for those fans, but like you mentioned there are quite some variables, one being build quality:)
very good fans (many of which are now on used parts market or ebay) was made for old Intel processors (like Pentium 4's and etc) in plastic glass reinforced but also with internal PWM sensor (smart fan mode) which changing speed as needed or temp change (only few 3D printer boards are have PWM sensory but anyway…)
