A noise muffler for the exhaust of waste gases from apparatus such as an oxygen concentrator, including a muffler core with an inlet to receive the waste gases and a plurality of bores in the core first to direct the waste gases through a filter material and a cap enclosing the filter material and forming a plurality of outlets to direct the waste gases out of the muffler, the bores and outlets positioned to cause the waste gases to change their direction of flow multiple times before exiting the muffler.