muttering vs murmuration

muttering and murmuration both are nouns.

Word	Noun	Adjective	Verb	Adverb
muttering	Yes	No	No	No
murmuration	Yes	No	No	No

As nouns, muttering and murmuration are synonyms defined as:

muttering and murmuration: a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech

Other synonyms of muttering include murmur, murmuring, mussitation, mutter.

muttering (noun)	murmuration (noun)
a complaint uttered in a low and indistinct tone	a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech
a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech