mouthpiece vs spokesperson

mouthpiece and spokesperson both are nouns.

Word	Noun	Adjective	Verb	Adverb
mouthpiece	Yes	No	No	No
spokesperson	Yes	No	No	No

As nouns, spokesperson is a hypernym of mouthpiece; that is, spokesperson is a word with a broader meaning than mouthpiece:

Other hypernyms of mouthpiece include interpreter, representative, voice.

mouthpiece (noun)	spokesperson (noun)
the aperture of a wind instrument into which the player blows directly	an advocate who represents someone else's policy or purpose
the tube of a pipe or cigarette holder that a smoker holds in the mouth
an acoustic device; the part of a telephone into which a person speaks
(especially boxing) equipment that protects an athlete's mouth
a part that goes over or into the mouth of a person
a spokesperson (as a lawyer)