The influence of installation effects, in particular, the bifurcations in anaero-engine bypass duct on noise radiation was investigated through high-orderaccurate three-dimensional numerical simulations. The physical process wasdescribed by a set of acoustic perturbation equations (APE), with a background meanflow. Four bifurcation arrangements, with an airfoil cross-section, were regularlyplaced in circumferential direction. Results were compared with those of a clean ductcase without bifurcations. A circumferential mode of m=12 with single radial mode ofn=1 and multi-n modes of n=1 to 5 at frequency of 1547 Hz were set as acousticinputs. Compared to the clean duct case, far field noise computations indicated 3.2 dBand 2.0 dB sound pressure level increases for single radial mode of n=1 and multi-nmodes respectively. Through this computational work, both near field propagationand far field radiation were studied to show the acoustic effects of bifurcationssuccessfully.