To become damp; to deaden.

deaden (a sound or noise), especially by wrapping

To restrain or deaden vibration. p. 28

To make damp or moist; to make slightly wet.

make moist; "The dew moistened the meadows"

To depress; to check; to make dull; to lessen.

check; keep in check (a fire)

lessen in force or effect; "soften a shock"; "break a fall"

smother or suppress; "Stifle your curiosity"

make vague or obscure or make (an image) less visible; "muffle the message"

To reinforce material in a system in such a way as to make it less prone to resonance. May include bracing or covering with a soft material.

reduce the amplitude (of oscillations or waves)