Centrifugal fans are machines that rely on the input of mechanical energy to increase gas pressure and discharge gas. They are a type of driven fluid machinery. Centrifugal fans are widely used for ventilation, dust removal, and cooling in factories, mines, tunnels, cooling towers, vehicles, ships, and buildings; for ventilation and induced draft in boilers and industrial furnaces; for cooling and ventilation in air conditioning equipment and household electrical appliances; for drying and sorting of grains; for providing wind sources in wind tunnels and for inflation and propulsion of hovercrafts, etc.

Direct-driven centrifugal fans have a lower noise level compared to belt-driven centrifugal fans. This is because direct-driven centrifugal fans adopt a direct driving method where the fan impeller is directly connected to the motor. By reducing the use of transmission components such as belts and pulleys, the potential sources of noise are reduced.

Belt-driven centrifugal fans use a belt transmission method to connect the fan impeller to the motor via a belt. Although belt transmission can provide greater flexibility and adaptability, some noise and vibration will be introduced during the transmission process, thus increasing the overall noise level.

It should be noted that the noise level can also be affected by other factors such as the design of the fan, the quality of materials, and working conditions. Different models and brands of centrifugal fans may have differences in noise performance. Therefore, when purchasing centrifugal fans, it is better to refer to the technical parameters and noise data provided by the fan suppliers in order to make accurate judgments and selections.