Design of Variable -Volume Resonant Mufflers

The purpose of this study is to solve the problem of exhaust pipe noise in the factory. By changing the length of the resonant volume, in order to control the maximum noise reduction frequency at the end of the pipe, a variable volume resonant muffler was designed. This maximum noise reduction frequency is in fact the resonance frequency, and depends on the size of the resonant volume. It seems to be that the resonance frequency noise decreases at the end of the pipe when the resonant volume absorbs its energy.
Under experimentation, different resonant volumes will change the resonance frequency. The bigger the volume, the lower the frequency, and on the contrary, the smaller the volume, the higher the frequency. When the lengths of the resonant volume are 60 mm,80 mm,100 mm,200 mm,300 mm,400 mm and 500 mm, the resonance frequency are 2004 Hz,1764 Hz,1544 Hz,1272 Hz,1148 Hz,1020 Hz and 880 Hz. According to this concept, a muffler can be designed to confine a wanted low frequency noise without largely changing the original exhaust ventilation system.