I would recommend considering using a 4-pin fans instead. The use of the 4-pin PWM solution helps meet acoustic targets in pedestal platforms through the baseboards ability to directly control the RPM of the fan.
Fan RPM is modulated through the use of an circuit located on the baseboard that send out a PWM control signal to the 4th pin of the connector, labeled Control.
3-pin fan are usually controlled by the thermistor located on the fan.