How can I slow down the devotee speed of my iMac (year 2003)?

Lately it's making to much rumpus, still it's not too warm contained by the room. I already tried to take adjectives the dirt.

How can I slow down the devotee speed of my iMac (year 2003)?

You could get a 220 volt aficionado and run it on 110. They have them at computer surplus stores. Or you could run 2 fan in series.