The main principle of diesel engine exhaust pipe is to use porous sound absorption material to reduce noise. The hindrance silencer is formed by fixing the sound absorbing material on the inner wall of the air passage or arranging it in a pipe in a certain way. When the sound wave enters the resistive muffler, a part of the acoustic energy is changed into the thermal energy dissipation in the pores of porous materials, and the sound wave through the muffler is weakened. The resistive silencer is like a pure electrical resistance circuit, and the sound absorbing material is similar to the resistance. Therefore, this muffler is called a hindrance muffler. The hindrance muffler has a bad effect on middle and high frequency noise elimination and low frequency noise reduction.