This seems to be somewhat troublesome with Linux in general: controlling the (cpu) fan speed. I recently bought a new mainboard with a not quite satisfying fan control via bios, so I switched to manual control and installed software solutions. While there is one excellent software for Windows - Speedfan - that gives the user complete control and a good interface, for Linux there seem to be only command line tools. Unfortunately they have one major flaw: Due to the missing interface it is difficult to identify the sensors that are connected to specific fans. Also I only found solutions for binding one sensor to one fan speed - ignoring the fact, that my dual-core cpu has to sensors with different temperatures.
Now I managed to reduce the fan speed to an acceptable noise, but it doesn't adjust to the temperature. I wich there would be a tool just similar to speedfan, where you can adjust the fans easily by mouseclick to see which sensors react... Would be great not only for Mint.