The effect of volute scattering on aerodynamic noise propagation of a centrifugal fan was analyzed. The theoretical result shows that full reflection of sound wave will occur on the air-steel volute interface when the incidence angle is more than 3.23 degree
but when the incidence angle is less than 3.23 degree
the A-weighted sound transmission loss is more than 42dB as long as the volute thickness is not less than 3mm. It seems that the volute could be regarded as an acoustic rigid boundary in noise prediction. A further numerical study was carried out by using a thin-body boundary element method(BEM)to analyze the influence of volute scattering on sound propagation. The numerical result shows that volute scattering has slight effect on low-frequency sound propagation and the fan low-frequency noise source can be viewed as a compact source. However
the effect of volute scattering on sound propagation is significant with the increase in sound frequency. The sound field generated by the distributed source in the centrifugal fan is distributed quite uniformly because of the diffuse reflection to the volute.
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