Comment 146 for bug 751689

As others have noted, the workaround is to set the fan to disengaged mode so that it runs at full speed. As for it previously being worse; in some cases it sounds like there may have been less dust in the fan at an earlier time, and in others, various changes over time may have caused the cpu to work harder and generate more heat. The bios is supposed to respond to more heat by ramping up the fan speed, but reports indicate this is broken and the bios won't go over 4000 rpm unless you override it with the disengaged state.