damper
damper (dam"pẽr) , noun
That which damps or checks;
(a)
A valve or movable plate in the flue or other part of a stove, furnace, etc., used to check or regulate the draught of air.
(b)
A contrivance, as in a pianoforte, to deaden vibrations; or, as in other pieces of mechanism, to check some action at a particular time.
Nor did Sabrina's presence seem to act as any damper at the modest little festivities.