As a kind of device to let the air flow through and reduce the noise, the muffler is installed in the pipe or the air inlet and outlet where the air flow through, which can effectively reduce the aerodynamic performance. There are many kinds of reactive muffler, which are mainly composed of expansion chamber muffler and resonant cavity muffler.
Expansion chamber muffler is also called expansion chamber muffler, which is composed of tube and chamber. It uses the expansion and contraction of pipe section to cause acoustic emission and interference pin sound.
The resonator muffler is composed of a section of pipe with several small holes and a closed cavity outside the pipe. The small hole and the cavity constitute an elastic vibration system. When the sound frequency of the air flow is the same as the natural frequency of the resonant cavity vibration system, the vibration system will produce resonance. The air column with a certain mass in the hole neck moves faster, the friction resistance increases, and a large amount of sound energy is converted into heat energy and consumed, so as to achieve the purpose of noise elimination.
The basic noise elimination unit structure has its own unique characteristics of noise elimination and aerodynamic performance. The expansion chamber muffler has better performance of low and medium frequency noise elimination, while the performance of high frequency pin is relatively low. There is also a certain problem of noise passing through the frequency. The solution is to use the method of internal inserted tube and multi expansion chamber in series. The effect of middle and high frequency pin noise of inner tube muffler is not good, but it has certain advantages in low frequency band, and can solve the problem of pass frequency noise in expansion chamber muffler. The resonator muffler has a good effect in the middle and high frequency band.