Suppressor

A suppressor, sound suppressor, sound moderator, or silencer, is a device attached to or part of the barrel of a firearm which reduces the amount of noise and flash generated by firing the weapon.

A suppressor is usually a metal cylinder with internal mechanisms to reduce the sound of firing by slowing the escaping propellant gas and sometimes by reducing the velocity of the bullet.

Battlefield 2
In Battlefield 2 suppressors were on the 3 avaliable pistols: the US's 92FS, the MEC's MR-444 and the PLA'S QSZ-92 and were avaliable on the Special Forces Kit and the Sniper Kit.

Battlefield: Bad Company
In Bad Company the suppressed weapons were the Submachine guns and two snipers which were the VSS and SVU.

Battlefield: Bad Company 2
In Battlefield: Bad Company 2 all engineer class weapons all had a silencernd with an exception of two sniper rifles which were like in Bad Company 1 the VSS and SVU.

Battlefield 3
It seems in the co-op gameplay video that the pistols were silenced at the start of presentation.