Abstract: A ductless noise attenuator is disclosed which includes a supply fitting mounted between an air conditioning unit and a recipient. The supply fitting blocks line-of-sight soundwaves using triangular-shaped protrusions on the inlet and outlet edges of a housing, and a diamond-shaped core which fits in the housing and has edges which extend to the space between the triangular-shaped edges of the inlet and outlet of the housing. The diamond-shaped core is composed of: two leading edges, which form a wedge with its point facing the housing inlet; and two trailing edges which is overlapped by the triangular protrusions of the housing. Finally, a return fitting conducts air back to the air conditioning unit while blocking line-of-sight soundwaves with a diagonal divider within a return housing. The design of the attenuator is intended to provide a minimum constriction on the airflow from the air conditioning unit, with a maximum of sound attenuation at audible frequencies by blocking line-of-sight soundwaves.