The noise of a cooling fan primarily comes from airflow, mechanical vibration, and motor operation. Airflow noise is caused by turbulence and vortices generated when the blades rotate and interact with the air. Mechanical vibration noise results from imbalances or bearing wear during fan rotation. Motor noise is generated by electromagnetic forces when current passes through the motor coils. Optimizing blade design, improving manufacturing precision, and using high-quality bearings can effectively reduce noise.