How control fan speed

Noisy fans are usually caused by dust sticking to the fan blades.If you have access to compressed air try blowing air backward through the fan. Be careful not to use too much pressure. Compressed air in a can works well. If you know what your doing opening the computer up and physically dusting the fan is another option.If not blowing out the fan by air flow running both in the exhaust and out the exhaust.a few times can get a lot of dust out.If the fan has run out of balance long enough it can actually damage the bearing and then the fan will need to be replaced. Hope this helps Good luck