A compressor includes a discharge chamber into which pressurized refrigerant gas is intermittently discharged. The pressurized refrigerant gas in the discharge chamber is sent to an external refrigerant circuit. A chamber for accommodating a resonance suppressing adapter is located between a discharge muffler and the external refrigerant circuit. The adapter includes a float valve and a spring. The float valve can move between a position connecting the accommodation chamber to the muffler and a position disconnecting the accommodation chamber from the muffler. The spring urges the float valve to its closed position. The force of the spring is determined such that the discharge pulse frequency of the refrigerant gas does not coincide with the natural resonance frequency of the external refrigerant circuit or at least such that the amplitude of pressure variations of the refrigerant gas is reduced.