Unsteady　flow　simulation　on　150mm　centrifugal　compressor　with　impeller-vaneless　diffuser-volute　configuration　is　carried　out.　Pressure　pulsations　at　observed　points　under　both　stationary　and　rotating　frame　are　transformed　into　frequency　domain　to　investigate　the　rotating　and　turbulent　noise　characteristics.　Spectrum　analysis　results　on　observed　points　under　stationary　frame　show　that　in　centrifugal　compressor　with　vaneless　diffuser,　dominating　noise　signals　are　related　with　the　pressure　pulsation　at　frequency　of　BPF,　which　is　caused　by　the　passing　of　each　impeller　blade.　Noise　signals　at　frequency　of　half　BPF　and　odd　order　multiples　can　also　be　observed　but　with　much　weakened　power,　and　as　a　result,　their　devotion　to　the　overall　noise　level　is　trivial.　Results　also　show　that　in　the　compressor　investigated　in　current　work,　the　main　sources　of　rotating　noise　locate　near　the　mid-streamwise　region　of　impeller,　with　pressure　pulsation　amplitude　reaches　the　level　of　7.1kPa.　Spectrum　analysis　on　pressure　pulsations　captured　under　rotating　frame　clarifies　that　noise　signals　are　dominated　by　wheel　passing　frequency,　which　are　caused　by　the　potential　flow　interaction　between　impeller　and　volute　tongue.　Meanwhile,　pressure　pulsation　strength　increases　as　the　distance　to　volute　tongue　decreases,　with　maximum　amplitude　reaches　about　5.1kPa　near　the　exit　of　the　impeller.　Anyway,　no　sign　of　noise　radiation　outside　of　centrifugal　compressor　is　captured　for　such　kind　of　pulsation,　hence,　they　do　not　contribute　the　compressor　radiation　noise.　©　The　author(s)　and/or　their　employer(s),　2012.