Pulse Width Modulation
The use of a 4 wire PWM controlled fans is a means to reduce the overall system acoustics. The expectation is a 4 wire PWM controlled fan when properly implemented will be significantly quieter than a similar 3 wire fan.
The Nexus 80MM PWM Series case fan has an extra big fan speed range. This allows the fan to be ultra quiet at low speed and provide massive air flow at full speed in case thing get too hot. Great control over a massive RPM range.
