A muffler for muffling engine operating sound and including a double-walled cylindrical shell closed at opposite ends by double-walled closure caps. The space between the shell walls is filled with sound-absorbing solid particles. The shell is partitioned into three axially contiguous chambers. A gas charging pipe projects through one closure cap and axially within the shell, and has two pairs of facing discharge elbows for discharging gas from the charging pipe at locations in the first chamber. A first pair of gas transfer pipes extends from the first chamber into the central chamber to points of opposed gas discharge. A second pair of gas transfer pipes extends from the central chamber into the third or discharge chamber, and from this location, the gas passes out of the muffler via a discharge pipe.
