There is also a natural wind "220V Cooling Fan", using computer simulations, also known as smart fan. It is stored in a microcomputer in many programs that like the same music signal, so that "220V Cooling Fan" of speed stops and time changes are irregular, resulting in "natural wind." The difference is that intelligent simulation can also produce several different "natural wind." It's like a piece of music before the keynote, but also adds a new melody, creating a "Variations", as that "220V Cooling Fan" speed grade and more irregular intervals, so that the wind sent fans closer to the natural wind, cool feeling people have left its natural environment.