The area between the air inlet and outlet of a cabinet accounts for 60% to 80% of the total system impedance. Besides, the greater the air flow, the higher the noise level. The higher the total system impedance, the more the air flow required for cooling. So, to minimize noise, the system impedance must be reduced to the lowest possible level.
Turbulence caused by obstacles encountered along the airflow path generates noise. Thus, any obstruction, especially in the critical inlet and outlet area, must be avoided to reduce noise.
Since a high-speed fan generates more noise than a low-speed one does, try and select a low-speed fan whenever possible. A larger, slower fan is very often quieter than a smaller, faster fan while delivering the same air flow.
The air flow required for cooling is inversely proportional related to the temperature rise allowed within the system. A slight increase in the allowable temperature rise leads to a significant change in air flow required. Thus, if there is a little compromise to the limit imposed on allowable temperature rise, the air flow required will be less considerably. Consequently, the noise is remarkably declined.
In some cases, the weight of a system is light, or the system is specified in certain operating methods. It is recommended to use a soft and flexible isolator to avoid vibration transmission.
Voltage variation will affect the noise level. The higher the voltage applied to the fan, the higher the speed, the greater the vibration, the greater the noise.
The design of every component of the fan affects the noise level. Following factors that affect noise must be considered while designing: the size of the winding core, the design of blade and frame, and accurate manufacturing and balance.