verb (v)

• deaden (a sound or noise), especially by wrapping(verb.perception)

  Synonym:
  damp, dampen, dull, muffle, mute
  

  source: wordnet30
• make less strong or intense; soften(verb.communication)

  Example:
  Tone down that aggressive letter.
  

  Synonym:
  moderate, tame
  

  source: wordnet30