The muffler's muffler principle is to use porous sound-absorbing materials to reduce noise, which is the principle of a resistive muffler. The sound-absorbing material is fixed on the inner wall of the airflow channel or arranged in a pipe in a certain manner to form a resistive muffler. When the sound wave enters the resistive muffler, a part of the sound energy rubs in the pores of the porous material and is converted into thermal energy to be dissipated, which weakens the sound wave passing through the muffler. A resistive muffler is like a purely resistive electrical circuit, and sound-absorbing materials are similar to resistors.