Silencers

Silencers are weapons modifications that don't work they way they sound. While there is a small amount of deadening of sound, the main purpose is the disguise the weapon. Most stations/worlds/populated areas with some form of security have monitoring systems in place to detect weapons fire. A silenced weapon is trying to evade weapons detection systems, but detection systems adapt and learn. So you might get a few shots before the alarms go off. So it's a back and forth battle between the detection systems and the people trying to circumvent them.