Noise radiating from rotating blades surrounded by a centrifugal volute is calculated combining a hybrid computational aeroacoustic method with the thin-body boundary element method (BEM), which considers the scattering effect of the volute to noise propagation. First, unsteady viscous flow in the centrifugal fan is simulated to obtain the noise sources information on the blades, and then the radiated noise in free field is computed using the Ffowcs Williams and Hawkings equation in the frequency domain. Lastly, the thin-body BEM is adopted to predict scattering effect of the volute. Good agreement between the numerical result and the exact solution of the plane wave scattered by a rigid flat plate validates the developed computational code. And the numerical result for blades noise shows that the scattering of the volute not only changes the directivity pattern of blades noise but also enhances the sound pressure level at the outlet of the volute.
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