24V DC Cooling Fan how to achieve low noise ?

The following guidelines provide a "24V DC Cooling Fan" users the best way to reduce the noise to a minimum
1. System Impedance: (SystemImpedance) a housing air inlet and the air outlet between the range accounting for the overall system impedance from 60 to 80%, in addition to the greater air flow, the noise is relatively higher. "24V DC Cooling Fan" system impedance is higher, the greater airflow required for cooling, so in order to minimize the noise, the system impedance must be minimized.
2. "24V DC Cooling Fan" disrupt airflow along the airflow path obstruction encountered while spoiler cause will produce noise. Therefore any obstacles, particularly in the critical range of air inlet and outlet must be avoided in order to reduce noise.