The muffler is a weight component of the automobile exhaust system. In terms of form, there are resistance (form), resistance (form) and compound. Among them, the resistive muffler is mainly composed of porous pipes and sound-absorbing fibers (sound-absorbing cotton). The sound absorption coefficient of the latter changes with the change of physical properties such as density and diameter, that is, the greater the fiber density, the smaller the diameter, and the higher the sound absorption coefficient. The value of the sound absorption coefficient is also related to the effect of the whole muffler. Of course, there are many factors that affect the noise elimination effect, such as the section circumference, effective length and section area of the muffler. The greater the circumference and effective length, the better the noise elimination effect.

How does resistive exhaust work?

There are porous tubes and sound-absorbing fibers in the resistive muffler. When the exhaust gas contacts with the fibers through the porous tubes, the latter generates vibration and heat energy due to friction and viscosity. Noise is converted in this process, so it is also called the sound absorption process.

The baffle muffler has the characteristics of small size, so most of the original cars like to use the baffle muffler in the middle drum. If you want to give full play to its muffler function, the installation position is generally closer to the direction of the engine. A large number of tests have shown that the damping effect of the resistive muffler on the middle and high frequency noise of the engine is better than that on the middle and low frequency noise. In the same case, the performance of resistant exhaust is just opposite to that of resistance.

reactive muffler 

The structure of the reactive muffler (also known as the reflective type) has no sound-absorbing cotton, and is mainly composed of a partition and an expansion chamber. Generally, the muffler has three expansion chambers with different sizes. Use exhaust gas to reflect and interfere with each other (friction) in these chambers to achieve noise elimination effect. Large chambers are more conducive to noise treatment, but their size is also limited by the shape of the chassis. In addition, due to the different working modes, the volume of the reactive muffler is larger than the resistance, so it is mostly installed at the rear of the vehicle. The obvious effect of noise suppression on medium and low frequencies has helped it win the favor of many original car manufacturers.

Composite muffler

As the name implies, the structure of the composite muffler combines the characteristics of the first two types of mufflers, that is, it has both sound absorption cotton and expansion chamber. As mentioned above, the two types of mufflers have different lengths when corresponding to the engine speed. The composite muffler well balances the two characteristics, with a wide range of corresponding, more flexible volume, but relatively high cost.