Abstract <p>The results of a numerical investigation of tone noise of a scale-model fan with ultralow tip speed under cutback and sideline operational conditions are presented. The investigation is performed using a method of calculation in the frequency domain, developed at the Central Institute of Aviation Motors (CIAM). The interaction between the rotor blades and stator vanes is taken into account. The fields of the flow pulsations in the near field and the distributions of sound pressure levels in the far field are obtained for both operational conditions. The data are compared with the results of the experiment conducted on the CIAM test rig. Satisfactory agreement between the results of the simulation and the experiment is shown. A qualitative similarity between the directivity diagrams obtained on the bases of computational and experimental data is observed. It is shown that the dominant source of tone noise is radiation from the nozzle. The obtained results are compared with those of the tone noise calculation of a fan with supersonic tip speed. It is shown that the directivity patterns of tone noise for the two fans differ qualitatively. It is found that the reason for this difference is the rotor rotation noise of the fan with supersonic tip speed.</p>