sound out vs say

sound out is not a noun while say is a noun.

Word	Noun	Adjective	Verb	Adverb
sound out	No	No	Yes	No
say	Yes	No	Yes	No

As verbs, sound out and say are synonyms defined as:

Other synonyms of sound out include articulate, enounce, enunciate, pronounce.

sound out (noun)	say (noun)
	the chance to speak

sound out (verb)	say (verb)
try to learn someone's opinions and intentions	express in words
speak, pronounce, or utter in a certain way	report or maintain
	speak, pronounce, or utter in a certain way
	express a supposition
	give instructions to or direct somebody to do something with authority
	communicate or express nonverbally
	recite or repeat a fixed text
	indicate
	state as one's opinion or judgement; declare
	utter aloud
	have or contain a certain wording or form