Abstract: 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 in the zone. A table coupled to the controller lists for each temperature value an optimum rotational rate for the fan, the optimal value being the minimal value of rotation rate for the fan to provide a sufficient ventilating of the zone at this corresponding temperature. The thermo-sensor when actual temperature in the zone is changed during operation, inputs this condition to the controller, which modifies the voltage, applied to the motor, to provide the assigned optimal rotation rate.