Which kind of centrifugal fan makes little noise

Centrifugal blowers and maglev centrifugal blowers produce relatively little noise during operation.
1, centrifugal blower: the principle of aeroacoustics and aerodynamics design, with low noise characteristics. In normal operation, because there is no mechanical friction, the noise generated is generally below 85dB, which is lower than the decibel of the sound of the traditional blower.
2, magnetic suspension centrifugal blower: due to the use of magnetic suspension bearing technology, centrifugal impeller, high-speed permanent magnet synchronous motor and special frequency converter, frictionless, oil-free operation can be achieved, and the efficiency is greater. Compared with traditional displacement Roots fan, energy consumption can be saved by 30%.