Abstract An experimental study is described to explore the dominant sound generation mechanisms of the spectral components governing the overall noise level of centrifugal compressors. At the design speed with supersonic flow conditions in the rotor blade channels, blade tone noise and buzz-saw noise are the main contributors. On the inlet, rotor-alone noise is the main source while rotor–stator interaction noise dominates on the outlet side in case of vaned outlet diffusers. Over a large range of rotor speeds with subsonic flow conditions, radial compressor noise is dominated by tip clearance noise which is produced by the secondary flow through the gap between rotor blade tips and the casing wall which in turn gives rise to the rotating instability phenomena observed earlier in axial-flow machines.