stress vs sound out

stress is a noun but sound out is not a noun.

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

As verbs, sound out is a hypernym of stress; that is, sound out is a word with a broader meaning than stress:

Other hypernyms of stress include articulate, enounce, enunciate, pronounce, say.

stress (noun)	sound out (noun)
the relative prominence of a syllable or musical note (especially with regard to stress or pitch)
(physics) force that produces strain on a physical body
(psychology) a state of mental or emotional strain or suspense
difficulty that causes worry or emotional tension
special emphasis attached to something

stress (verb)	sound out (verb)
to suffer from stress	try to learn someone's opinions and intentions
to stress, single out as important	speak, pronounce, or utter in a certain way
put stress on; utter with an accent
test the limits of