Bullet is a 4-inch round repackable bullet, 4-inch x16-inch round T304 stainless steel repackable muffler with 2.25-inch, 2.50-inch or 3-inch free flow spiral straight through core wrapped in stainless steel mesh. In the original sound field, the electronic device is used to generate an equal width and inverse sound wave, so that the sound wave can offset the original sound field within a certain range. The muffler is mainly composed of microphone, amplifier, phase shift device, power amplifier, loudspeaker, etc.