The method used with this muffler to reduce noise is mainly absorption. The pulses have to travel through the muffler twice, which basically makes the muffler twice as long with twice the sound killing power. Also some acoustical tuning goes into making a muffler like this as well. With brass wind instruments, you change the note by selecting different length tubes for the air to travel. Longer tubes will give a deeper note while shorter tubes give a higher note. This type of muffler basically lengthens the tube, allowing sound waves to spread out and emit a deeper tone once exiting the system. The twin-pass design flows as well as a straight-through but will sound much quieter.