Numerical simulation of the effect of geometric parameters of silencer on its acoustic performance

In this study, a three-dimensional numerical simulation of turbulent flow inside a sound attenuator was conducted to investigate and control the outlet sound. The analysis was performed using the finite volume method and ANSYS software. The aim of this research was to examine the effect of geometric parameters on the sound pressure difference between the inlet and outlet of the sound attenuator. The geometry of the diffuser and the use of rock wool, which is a type of sound absorber, have a significant impact on reducing the outlet sound, as most standards, including the AMCA standard, specify that the sound level at a distance of 1 meter should not exceed 85 dB. In this study, four geometric parameters were evaluated, including the diameter of the diffuser holes, the spacing between the holes, the number of holes, and the length of the rock wool region. The results indicate that increasing the diameter of the diffuser holes, the spacing between the holes, and the number of holes leads to higher sound jets exiting the diffuser holes and lower flow energy, resulting in a reduction in the sound pressure difference between the inlet and outlet of the sound attenuator. Additionally, increasing the length of the rock wool region increases the length of the flow path and consumes more sound energy, ultimately resulting in a greater reduction in the sound pressure difference. In conclusion, the maximum reduction in sound pressure difference is associated with a hole diameter of 10 millimeters, a hole spacing of 30 millimeters, a number of holes of 20, and a rock wool length of 1400 millimeters.