Sound attenuator for a fluid flow line and method of manufacturing the same

A sound attenuator (10) for a fluid flow line, comprising a unitary one piece inner pipe (12) and a unitary one piece outer pipe (14) coaxially encompassing the inner pipe (12), the outer pipe (14) having a length and an inner surface that is spaced radially from an outer surface of the inner pipe (12) over a major part of the length of the outer pipe (14), the outer pipe (14) having first and second constriction sections (141) of reduced diameter and spaced apart from each other axially, the inner pipe having first and second expansion sections (121) expanded outwardly to define an enlarged diameter at axial locations corresponding respectively to the first and second constriction sections (141) of the outer pipe (14), the inner surface of the outer pipe (14) at the first and second constriction sections (141) being connected directly to the outer surface of the inner pipe (12) at the first and second expansion sections (121) respectively to form at least one axially and radially outwardly closed ring chamber (16), at least one opening (18) being formed through a wall of the inner pipe (12) between the first and second expansion sections (121) so that an interior of the inner pipe (12) is in fluid exchanging contact with the ring chamber (16), wherein the outer pipe (14) further comprises a third constriction section (141) and the inner pipe (12) further comprises a third expansion section (121), the inner surface of the outer pipe (14) at the third constriction section (141) being connected directly to the outer surface of the inner pipe (12) at the third expansion section (121);

• and the first and third constriction sections (141) and the first and third expansion sections (121) associated therewith are arranged in an area of two axial ends of the outer pipe (14).