valid application_number US 201314387375 A description a muffler illustrated in fig1 has a muffler housing 1 2 with a housing wall 1 1 the housing wall 1 1 defines an interior space 6 in which an inlet pipe 2 with the outflow openings 2 1 2 2 and two outlet pipes 4 1 4 2 are shown each with an inlet opening 4 5 4 6 the inlet pipe 2 and the outlet pipe 4 1 4 2 discharge via the outflow opening 2 1 2 2 or respectively via the inlet pipe 4 5 4 6 into the coupling chamber 3 a 3 b the coupling chamber 3 a 3 b together with the inlet pipe 2 and the respective outlet pipe 4 1 4 2 forms a flow channel 3 3 3 4 of the outflow opening 2 1 2 2 of the inlet pipe 2 to the inlet opening 4 5 4 6 of the outlet pipe the inlet pipe 2 is guided in the axial direction to a centre axis 1 5 of the muffler housing 1 2 through the housing wall 1 1 and mounted with an open end 2 6 within the housing wall 1 1 the inlet pipe 2 has four outflow openings 2 1 2 4 which are designed as perforation zones with the space of all outflow openings 2 1 2 4 whereby the space of all outflow openings 2 1 2 4 i e the opening cross section ai of the perforation zones 2 1 2 4 within a coupling chamber 3 a 3 b.