muffle vs tone down

muffle is a noun but tone down is not a noun.

Word	Noun	Adjective	Verb	Adverb
muffle	Yes	No	Yes	No
tone down	No	No	Yes	No

As verbs, muffle and tone down are synonyms defined as:

Other synonyms of muffle include damp, dampen, dull, mute.

muffle (noun)	tone down (noun)
a kiln with an inner chamber for firing things at a low temperature

muffle (verb)	tone down (verb)
suppress in order to conceal or hide	make less strong or intense; soften
deaden (a sound or noise), especially by wrapping	deaden (a sound or noise), especially by wrapping