I am not sure it will work for all.
I have an t540 with the same problem.
My problem was solved by editing the Bios Power Management seetings. On the menu item :Power > Adaptive Thermal Management
Scheme for AC: Balanced Scheme for Batery: Balanced
I choosed balanced instead of Maximum performance for both AC adapter and Batery.
After this, re-start the system and no more fan noise from time to time. To enter the bios, just type enter during startup.
Now the Fan stays around 2000 with normal usage. I am not sure this is high or low. But it is not noisy. If you stop using many programs the fan can just go down to 0 rpm. When you activate any program again the Fan goes up to 2000 rpm or more (depending on the CPU usage of the application) and then stays at this level.
One tip is to install the lm-sensor and psensor to monitor your fan and CPU temperatures.
I will monitor my fan from now and if any thing change I will post aother reply.
All the best, Gustavo