Did you upgrade the BIOS recently?
According to the BIOS release notes the default fan duty has been increased twice:
BIOS 036: "Changed default Fan duty to 30%."
BIOS 039: "Changed default fan duty to 40%."
I also find the fan noise of the NUC a little disappointing. It is not very loud, but a somewhat irritating high pitch sound.
It is possible to change the default back to 20% and you can also modify other fan parameters in the BIOS settings. But of course you have to be careful not to overheat the device.
Another post about the NUC fan that could be interesting for you:
Another option might be to replace the NUC case with one of the fan-less cases that are available now.
I only upgraded the bios to BIOS 039 after the noise started getting to me. But for some reason the fan settings are still at 78, 20 . There is a quiet option of 81, 40. I seem to be on a Custom setting. I can't stand whiny fans and the NUC has been great untll now. I also have a new Mac Mini i7 system which I never hear unless really push it but even then the fan is not whiny.
I did have a look at that other thread which was really interesting. Unfortunately it doesn't apply to me.
I would gladly get another case, but are there passive solutions for the i3 NUC? I know Shuttle is coming out with their DS47 passive solution. It uses a Celeron 847.
Odd as the NUC has been perfect until recently. Hope it's a simple fix. I am very adverse to tiny fans.
Any suggestions re a passive case?
Thank you. I seem to only be able to buy the Tranquil PC case ( all the cases seem to be in Europe or aren't out) for shipment to Canada. Very tempting except for the wireless issue. Perhaps I should wait for the Silverstone case which looks very nice. I found a couple of others but they are not ready yet are are from Europe so ordering may be an issue. I didn't think an i3 could be fanless but those cases claim to be even better than the default case.