(EN) The present invention relates to a method of producing a pipe provided with at least one vibration attenuator in the form of a by-pass conduit portion. The method is characterised in that it consists in providing a preform, arranging said preform in an open mould and insufflating an expansion fluid under pressure into this preform while its constituent material is still at a temperature close to its glass transition temperature, closing the mould, when the preform has reached a predetermined degree of radial expansion, so as to simultaneously form the walls (l' and 2') of said circulation pipe (1) and of the by-pass conduit or pipe portion (2), and solid plate portions (3) connecting the pipe (1) and the pipe portion (2), extracting said unit [pipe (1)/by-pass pipe portion (2)] from said mould after solidification and, finally, attaching or forming connecting and branching pieces at the two opposing ends of the circulation pipe (1).
