Is your fan loud when BOINC is running?

I always have BOINC running 100% all of the time. The fan just kinda gently humms in the background. When the room is very quiet, if i shut down the fan, then i hear silence. But i don't really mind the humm from the fan.

Not really. It gets loud periodically but I think thats just to get the hot air out, then it fades into silence again.

Its definitely not as annoying as the continuous hum of the refridgerator.

If you have system monitoing software installed, you can see which BOINC projects cause more heat than others.

Although not a BOINC application, Prime95 is notorius for really getting the system going! In fact it's often used for hardware stress tests. Not recommended for a laptop, where the airflow around the machine is critical.

Nowadays we can set the percentage CPU time to allocate to BOINC, in order to moderate the amount of heat generated. You'll be able to see the impact of this in task manager (or similar). If it stays stuck at 100% then you'll likely not have the fan changing speed, but risk overheating.

Dust is the enemy of your system's cooling. I've had one of my early model computers (a 386 or 486, if I recall) completely pack up after the heatsink fan got clogged with dust.

It seems the ideal situation for a quiet machine is to choose one of the less stressful projects (CPDN is quite good here - but not so generous with point allocation) and have it in a dust-free, low temperature environment like an air-conditioned room.