repress vs muffle

repress is not a noun while muffle is a noun.

Word	Noun	Adjective	Verb	Adverb
repress	No	No	Yes	No
muffle	Yes	No	Yes	No

As verbs, repress and muffle are synonyms defined as:

Other synonyms of repress include smother, stifle, strangle.

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

repress (verb)	muffle (verb)
block the action of	suppress in order to conceal or hide
put out of one's consciousness	deaden (a sound or noise), especially by wrapping
suppress in order to conceal or hide
put down by force or intimidation
impede or hinder the natural development or self-expression of