sounding board vs actor

sounding board and actor both are nouns.

Word	Noun	Adjective	Verb	Adverb
sounding board	Yes	No	No	No
actor	Yes	No	No	No

As nouns, actor is a hypernym of sounding board; that is, actor is a word with a broader meaning than sounding board:

sounding board: a person whose reactions to something serve as an indication of its acceptability
actor: a person who acts and gets things done

Other hypernyms of sounding board include doer, worker.

sounding board (noun)	actor (noun)
(music) resonator consisting of a thin board whose vibrations reinforce the sound of the instrument	a theatrical performer
a person whose reactions to something serve as an indication of its acceptability	a person who acts and gets things done