muffle vs tone down

muffle

verb
  • To mute or deaden (a sound etc.). 

  • To wrap (a person, face etc.) in fabric or another covering, for warmth or protection; often with up. 

  • To wrap up or cover (a source of noise) in order to deaden the sound. 

noun
  • The bare end of the nose between the nostrils, especially in ruminants. 

  • A machine with two pulleys to hoist load by spinning wheels, polyspast, block and tackle. 

  • A kiln or furnace, often electric, with no direct flames (a muffle furnace) 

  • Anything that mutes or deadens sound. 

  • A warm piece of clothing for the hands. 

tone down

verb
  • To relax; to make quieter or less obtrusive; to make milder. 

  • To make a television program, piece of writing, etc. less offensive and so more suitable for a family audience. 

  • To moderate or relax; to diminish or weaken the striking characteristics of; to soften. 

How often have the words muffle and tone down occurred in a corpus of books? (source: Google Ngram Viewer )