A dampening field or damping field was an energy field which interfered with power emissions within its effective range of operation. Dampening fields could drain an area of power, interfere with communications, block sensor readings including transporter locks, and prevent the operation of phasers and other large power systems.
Dampening fields were employed by a wide variety of species in varying circumstances for varying reasons.
The Vulcan's Forge was protected by a dampening field; a reason the Syrrannites hid in the Vulcan's Forge. (ENT: "The Forge")
In 2369, the damping fields of the runabout USS Ganges were barely operating after the ship returned from a routine mission into the Gamma Quadrant and was forced to return to the station due to a power failing. (DS9: "Q-Less")
A broad band damping field was able to block the communication from a penal moon with starships. (DS9: "Battle Lines")
In 2371, Tolian Soran erected a dampening field around his laboratory on the Amargosa observatory so no one would discover his plan to annihilate the Amargosa star. (Star Trek Generations)
Cardassian space stations are often equipped with a dampening field before they are abandoned, thus trapping anyone who boards the station, rendering them unable to communicate with those outside. (DS9: "Empok Nor") Similarly, the Voth and Night Aliens employ large-scale dampening fields capable of rendering entire starships powerless, mitigating any danger they may pose. (VOY: "Distant Origin", "Night")
Tactically, dampening fields may be used in coordination with transporter scramblers or to prevent the use of phasers and other energy weapons. The threat posed to operations by dampening fields was sufficient for the Federation to develop the TR-116 rifle as an alternative to phaser rifles, but only one prototype was built and the weapon was never regularly used by the Federation. (DS9: "Field of Fire")
After being marooned inside an energy barrier on Ledos in 2378, Seven of Nine used the deflector array from her downed class 2 shuttle to generate a dampening field to neutralize the barrier's source. (VOY: "Natural Law")