Various implementations include a muffler including a shell and a tube assembly. The shell defines a shell cavity and has a shell longitudinal axis, a shell first end, and a shell second end. The shell first end and the shell second end each define a shell opening extending to the shell cavity. The tube assembly is disposed within the shell cavity. The tube assembly includes three or more nested tubes. Each of the three or more nested tubes has a tube longitudinal axis parallel to the shell longitudinal axis, a tube first end, and a tube second end. Each of the three or more nested tubes defines a plurality of perforations. The three or more nested tubes are disposed circumferentially adjacent each other around the shell longitudinal axis such that portions of sides of the three or more nested tubes form an open portion extending along the shell longitudinal axis.

Method for producing a fibrous mat, which can be installed in a component of a vehicle provided with an internal combustion engine for acoustically and thermally insulating the component. The method comprises the steps of: providing a fibrous core consisting of at least one fibrous bundle that extends along a direction that is approximately parallel to a longitudinal axis; wrapping the outer surface of the fibrous core by means of a fibrous bundle that extends along a direction that is approximately transverse to the bundle of the fibrous core, thus providing at least one outer tubular fibrous containment sleeve that extends, in turn, along the longitudinal axis and covers the outer surface of the fibrous core to trap the fibrous core therein.

Provided are an inorganic fiber-formed article having both high basis weight and excellent peel strength and a mat for an exhaust gas cleaning apparatus and an exhaust gas cleaning apparatus including the inorganic fiber-formed article. The inorganic fiber-formed article includes inorganic fibers and needle marks extending in the thickness direction and including vertical bundles composed of the inorganic fibers extending in the thickness direction, in which the average volume of the vertical bundles per needle mark measured by a prescribed peel test is 1.0 mm.sup.3 or more.

A pipe (11), carrying exhaust gas, of an exhaust system (1) of an internal combustion engine (9), with a tubular body (15) carrying exhaust gas, and with at least one attachment part (12) separate with respect to the tubular body (15), which is added laterally to the tubular body (15) so that externally on the tubular body (15) a cavity (13) is arranged delimited at least partially by the attachment part (12), which extends in the circumferential direction (14) of the tubular body (15) over less than 360.

An exhaust duct assembly for conveying exhaust gases emanating from a combustion zone to atmosphere is disclosed. The assembly includes: an exhaust gas outlet for exhausting exhaust gas into the atmosphere; and an acoustic duct portion located upstream of the exhaust gas outlet, the acoustic duct portion having a peripheral wall defining a through-passage arranged and constructed to promote propagation of sound there-through. The acoustic duct portion has a length in a flow direction that is at least 50% of an average hydraulic diameter of the through-passage.