Due to the high speed "220V AC Cooling Fan" greater than the low speed fan noise, so you should try and use low-speed fans as possible. And a large size, low speed fan, generally, quieter than the small size, high speed fan when transporting the same air volume. "220V AC Cooling Fan" temperature within a system, is inversely proportional to the amount of air required for cooling temperature and allowed. Allowable temperature rise slightly increased, to a significant reduction in the required amount of wind. Therefore, if "220V AC Cooling Fan" impose the allowable limit temperature rise slightly relax, will reduce the required amount of wind noise can be reduced.