The suppressor reduces the noise and muzzle flash generated by the firearm, and prevents the player from showing on the minimap when firing. Bullet velocity and effectiveness at range are reduced.
Suppressors mask your location on the minimap when firing, reduce muzzle flash, and reduce the volume of the weapon. (Note that outside of 40 meters of the target one does not show up on the minimaps when firing.) Bullet velocity is reduced by 20% at best estimates. Effectiveness at range is greatly reduced, in that the range of maximum damage is reduced by 10 meters and range of minimum damage is reduced by 25 meters.
This is recommended for Infiltrators firing at close to medium distances or anyone who intends on getting behind enemy lines. The key to this attachment is maintaining the element of surprise and eluding enemy detection.
Due to the decreased bullet velocity at ranges further than 150+ metres, a suppressor on long range sniper rifles (bolt actions), is not a viable choice, as it greatly increases the amount of bullet drop. However, a suppressed sniper rifle can still kill instantly with a headshot.