From Dictionary.com
Damping
damp·ing (dmpng)
n.
The capacity built into a mechanical or electrical device to prevent excessive correction and the resulting instability or oscillatory conditions.
damp·en (dmpn)
v. damp·ened, damp·en·ing, damp·ens.
v. tr.
To make damp.
To deaden, restrain, or depress: ?trade moves . . . aimed at dampening protectionist pressures in Congress? (Christian Science Monitor).
To soundproof.