Dampen

v. 1 make or become damp. 2 (often foil. by down) = DAMP v. 2a. damper n. 1 discouraging person or thing. 2 device that reduces shock or noise. 3 metal plate in a flue to control the draught. 4 Mu& pad silencing a piano string. put a damper on take the vigour or enjoyment out of.