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

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

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

It should be noted that the noise level will also be affected by other factors, such as the design of the fan, material quality, working conditions, etc. 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 fan suppliers in order to make accurate judgments and choices.