Did you add media to it lately?
Perhaps it's doing audio analysis or thumbnailing..
I added ~130 files a week or so ago by manual import. (The files are on a NAS.) I checked settings and found no reason for MC to be doing analysis now.
I was not comfortable disassembling the Id far enough to see whether there was anything hitting the fan. The noise seems to be loud when fan speed is high.
I think I have a solution to my fan noise problem. The original Bios settings seem to have changed after system hangups and/or power glitches. The fan controller was set to zero speed initially. The heat sink was not able to produce enough cooling and the temperature rose to the point where the fan kicked it at maximum speed.
I spent a lot of time watching temperatures with the Id in the Bios and then doing experiments with the fan controller settings. I've found some settings that seem to produce a quiet system.
Fan Control Mode = Custom
Minimum Duty Cycle = 27% The fan runs at ~ 2400 RPM initially with that setting. It can be heard 2 feet away but isn't very loud. It can't be heard from 10 feet away.
Primary Temperature = Motherboard
Minimum Temperature = 47 degrees C (defines the temperature that fan controller will attempt to maintain.)
Duty Cycle increment = 4 %. (controls how much fan speed is increased as temperatures rise at the sensors.)
Most of the time this works fine. However, sometimes the fan begins running at top speed and does not stop until I shut the Id down. I have not been able to reproduce this behavior at will.
Some notes for others who have a noise problem:
1. Minimum Duty Cycle sets the minimum fan speed when the temperatures of the sensors are low. It also affects the fan speed at higher temperatures. A setting of 0 % keeps the fan from running when temperatures are low. However, once the fan controller decides to turn on the fan, the fan will run at maximum speed (~ 4000 rpm which as quite loud.)
2. Minimum Temperature settings above ~55 degrees are not honored by the fan controller.
3. The room temperature in my home office has been a few degrees about 80 degrees F while I tested. The Id NUC does not have enough heat sink capacity to keep motherboard and memory temperatures to an acceptable level without the fan running.
4. If the noise level from your NUC based Id becomes bothersome, restart the Id and press F2 on the keyboard to enter the Bios. Click on "Advanced" and then click on "Cooling". Watch the temperature and fan speed graphs and check settings. If you don't want to make custom settings, the "Quiet" mode keeps the Id pretty quiet. The "Balanced" mode is a bit louder.
Jim and Bob, thanks for the help. I'll put the Id back in my system where it is headless and see whether I continue to have a problem.