articulate vs sound out

articulate is an adjective but sound out is not an adjective.

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

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

Other synonyms of articulate include enounce, enunciate, pronounce, say.

articulate (adjective)	sound out (adjective)
expressing yourself easily or characterized by clear expressive language
consisting of segments held together by joints

articulate (verb)	sound out (verb)
speak, pronounce, or utter in a certain way	try to learn someone's opinions and intentions
express or state clearly	speak, pronounce, or utter in a certain way
put into words or an expression
provide with a joint
unite by forming a joint or joints