"220V Cooling Fan" chassis structure is not close: hard contact with the chassis bracket does not close, or too thin steel chassis, easy to send some annoying noise. Noise may be caused by the power supply fan on the chassis and power supply are not closely matched. Power "220V Cooling Fan" caused by the rotation of the chassis resonance. In addition, other hardware installed inside the chassis can cause unstable vibration. Low temperature cold: Some fans inside using a grease winter temperature is low, the fan inside the solidified grease in just machines "220V Cooling Fan" lower bearing part of the temperature, the viscosity of grease large rotational resistance big, big voice.