US Patent 7988427 Compressor muffler

A compressor has first (26) and second (28; 30) enmeshed rotors rotating about first (500) and second (502; 504) axes to pump refrigerant to a discharge plenum (42). The compressor includes a muffler system (200) comprising a sound absorbing first element (232) and a sound absorbing second element (236). The second element at least partially surrounds the first element and defines a generally annular flow path portion (230) between the first element and the second element. A wall (250) at least partially surrounds the second element. A space (259) optionally containing a sound absorbing third element (261) surrounds the wall.