The muffler's noise reduction principle involves the appropriate combination of cavities and tubes to achieve two functions for noise suppression:

Firstly, utilize the abrupt change in pipeline cross-section (i.e., the change in acoustic impedance) to reflect the sound waves propagating along the pipeline back towards the source, thereby causing the acoustic energy to be reflected back to its original location.

By utilizing reflections across several interfaces, the originally forward-propagating sound wave returns to its starting point and then bends back forward again. This point meets with the two other forward-propagating sound waves that have not yet been reflected, and they are equal in amplitude and differ by odd multiples of 180 degrees in phase, leading to their interference and cancellation.