Apparatus and method for reducing fan noise in a personal computer having at least one fan with a direct current motor. The fan is disposed within and ventilates a zone. Operative voltage is applied to the motor through a controller from a power supply. Thermo-sensors in the zone measure the temperature...http://www.google.com/patents/US6340874?utm_source=gb-gplus-sharePatent US6340874 - Method and apparatus utilized in computer type systems for control of variable speed fans to reduce their noise
