Definitions of dampen:

• verb:   lessen in force or effect
• verb:   check; keep in check (a fire)
• verb:   make vague or obscure or make (an image) less visible
• verb:   reduce the amplitude (of oscillations or waves)
• verb:   smother or suppress
• verb:   make moist
• verb:   deaden (a sound or noise), especially by wrapping