Noise Reduction in Centrifugal Fans by Use of Resonators

摘要

The significant reduction of aerodynamically generated blade passage noise at the source by mounting a lambda/4 resonator at the cut-off lip on centrifugal fans is considered. While preserving the original cut-off lip geometry, the perforated mouth of the resonator now forms the lip. The resonator can be tuned to various frequencies, e.g. the blade passage frequency, via a moveable end plug, enabling reductions in tone intensity of up to 29 dB. Attenuation of a somewhat lesser degree occurs within a frequency band about the resonance frequency. The bandwidth of the resonator response is influenced by the porosity of the resonator mouth.