Numerical investigation of the effect of baffle plate numbers in suppressor on flow and sound characteristics at firearms

Although it is impossible to completely eliminate the sound that occurs during firing for firearms, reducing this sound to a reasonable level may prevent understanding where the shot took place or provide gains such as not being able to understand whether the sound belongs to a firearm. Within the scope of this study, the effect of subsonic and supersonic bullets on the sound level of a gun firing 9x19 mm bullets was experimentally investigated. Then, the experimental results were compared with numerical results. Finally, the effect of the number and distance of the baffle plates in the suppressors used to reduce the explosion sounds on the flow field and far field noise levels was numerically investigated. Calculations were carried out in two-dimensional axisymmetric, transient conditions and Ffowcs Williams and Hawkings acoustic analogy (FW-H) equations were solved to predict the far-field noise. Nine cases including a gun without suppressor, a suppressor without baffles, one, three, and five baffles which were placed at 20 mm intervals from the suppressor inlet, and one, three, five, seven, and nine baffles which were placed with equal intervals in the suppressor were simulated and compared; generations of noise during the shooting process were analysed. The results showed that in case of without suppressor the sound pressure level was 156.1 dB at 2.5 m distance, while this value decreased nearly 6% in case of seven baffle suppressor which have an average value of 144.2 dB. The results obtained here may provide a beneficial reference for predicting the muzzle noise and optimizing the number of baffles in suppressor for small caliber gun systems.