trill vs sound out

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

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

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

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

trill (noun)	sound out (noun)
a note that alternates rapidly with another note a semitone above it
the articulation of a consonant (especially the consonant `r') with a rapid flutter of the tongue against the palate or uvula

trill (verb)	sound out (verb)
sing or play with trills, alternating with the half note above or below	try to learn someone's opinions and intentions
pronounce with a trill, of the phoneme `r'	speak, pronounce, or utter in a certain way