The present invention relates to a fan (300) comprising an impeller (301) and a housing (302) encasing the impeller (301), wherein the housing (302) comprises at least one inlet (303) for fluid to the impeller (301) and at least one outlet (304) for fluid from the impeller (301). The housing (302) further comprises at least one acoustic attenuation element (305) associated with the at least one inlet (303), the acoustic attenuation element (305) comprising at least one hollow lateral expansion (306; 307) arranged around the at least one inlet (303). The at least one hollow lateral expansion (306; 307) is open towards the at least one inlet (303) and is closed towards a periphery of the at least one acoustic attenuation element (305), so as to be configured as an acoustic resonant cavity for noise generated by the impeller (301). The acoustic attenuation element (305) further comprises at least one separation element (308; 309) in the at least one hollow lateral expansion (306; 307) configured for defining at least one second separated volume (310; 311) within the at least one hollow lateral expansion (306; 307), the at least one separation element (308; 309) being configured for dissipating an acoustic field within the at least one hollow lateral expansion (306; 307)
