A BIOS update regarding this issue is necessary. The Studio fan for the GPU and CPU is programed to work only when it needs to bring the temperature down by a few degrees (41c back down to 35-36c). In a quiet environment, like a classroom, it is quite annoying. Also by idling the fan, even if no programs are running the temperature rises and the system fan will kick in.
Make it so the fan will run at a constant AND quiet speed to keep the temperature from going up to high in the first place and the fan running at high RPM, resulting in a lot of noise.
I have two Dell laptops: Studio 15 and XPS M1530. Some time ago, the first one started to produce unusual heat and noise... I checked all possible causes, including RAM modules, system settings and whatever i found on this forum or Dell site. No result. Eventually, I used Dell Diagnostic Tool and it showed an error about FAN speed. It seems that it can't turn off or slow down the fan. XPS M1530 doesn't have such problem, the fan speed raises gradually, not just WIZZZ as in Studio... and it's not so fast. There is an option in Fan Diagnostics settings to set your own speed for high and low mode. I tried those from my XPS and it worked. There was no error during test and fan worked as it should. But I can change these speeds only for testing time... When i reboot the machine they remain incorrect. There must be some mistake in BIOS or other part that manages fans I think... Could anyone who has an Studio 15 check if that's the case? When you run Dell diagnostic tool (from USB or cdrom, or HD diagnostic partition) you can choose a custom check and then find a FAN diagnostic.
I know this is a very old thread, sorry for bringing it back up, but 2 years later and it appears like the Studio 15 still does this. I have a 1555 with a Core 2 Duo T6500 processor. The fan stays off much of the time, and then suddenly kicks up to one of the 4-5 set speeds. This is very annoying, it would be a much better auditory expirience if it ramped up slowly and gradually instead of all of a sudden. I have the latest BIOS installed.
Its not just the studio line. My Vostro 3300's fan comes on in a rush, then ramps back down to a quieter level. It does this on a regular basis even with no applications running. I have the latest BIOS installed.