Abstract: Provided is an expansion-chamber muffler as a downsized sound muffler while keeping a function of noise reduction, comprising: a tube (A) which supplies and evacuates a gas having a noise, wherein the tube (A) in the midway has a cavity with a cross-sectional area larger than that of the tube (A); and at least two or more ports for inflow or outflow of the gas on the lateral side of a tube (B) extending from the expansion-chamber muffler, on the opposite side of the noise source generating the noise.

Abstract: Provided is an expansion-chamber muffler as a downsized sound muffler while keeping a function of noise reduction, comprising: a tube (A) which supplies and evacuates a gas having a noise, wherein the tube (A) in the midway has a cavity with a cross-sectional area larger than that of the tube (A); and at least two or more ports for inflow or outflow of the gas on the lateral side of a tube (B) extending from the expansion-chamber muffler, on the opposite side of the noise source generating the noise.

Abstract: Provided are an expansion-type silencer (10) including a substantially rectangular parallelepiped-shaped expansion chamber (16) surrounded by six partition walls and having a suction port (20) and an exhaust port (22) which are formed in the partition walls, and an oxygen concentrator using the expansion-type silencer (10). The expansion-type silencer (10) has a rib (24) extending from one of the partition walls of the expansion chamber (16) formed with the exhaust port (22) toward the interior of the expansion chamber (16) while being in contact with both of a pair of parallel partition walls adjacent to the one of partition walls. The rib (24) is formed with an air passage (26) for providing communication between the exhaust port (22) and the expansion chamber (16).