Abstract: A compressor for compressing a gas comprises an impeller wheel mounted within a housing (2) defining an inlet (8) and an outlet (6). The inlet (8) has a plurality of apertures (20) in the form of bores or grooves defined in its surface that serve as an integral silencer. The inlet (8) may comprise a map-width enhanced structure (4) with the bores provided on one to a number of surfaces. The design provides for a compact and efficient compressor with noise reduction such that higher pressure ratio designs may be adopted. The apertures (20) may be provided in the housing (2) that defines the inlet (8) or in a separate insert.