Genuine Daikin 138233J Outdoor Muffler is the muffler in the outdoor refrigerant circuit that dampens the pulsation and flow noise the refrigerant makes as it moves through the system. When it fails or blocks, the unit may grow noisier, or lose output if flow is restricted. A genuine muffler fits and flows the way your Daikin expects, keeping the circuit quiet and clear — where a non-genuine part can restrict flow or pass noise.