A refrigeration system employing carbon dioxide, or the like, as refrigerant of which the pulsation of pressure is reduced sufficiently. The refrigeration system (1) comprises a compression mechanism (11), radiators (13, 31), expansion mechanisms (15, 17), evaporators (13, 31), and a p type muffler (20). The p type muffler has a first silence space (201), a second silence space (202), and a first communication path (203). The first communication path allows communication between the first silence space and the second silence space. The Pi type muffler is incorporated in at least one of the section between the refrigerant delivery side of the compression mechanism and the inlet side of the radiator and the section between the outlet side of the evaporator and the refrigerant suction side of the compression mechanism. The length of the first communication path is shorter than c/2ft, wherein c is sound velocity in the refrigerant and ft is a target reduction highest frequency.