sharp-eared vs hearing

sharp-eared is not a noun while hearing is a noun.

Word	Noun	Adjective	Verb	Adverb
sharp-eared	No	Yes	No	No
hearing	Yes	Yes	No	No

sharp-eared (noun)	hearing (noun)
	the act of hearing attentively
	(law) a proceeding (usually by a court) where evidence is taken for the purpose of determining an issue of fact and reaching a decision based on that evidence
	the ability to hear; the auditory faculty
	a session (of a committee or grand jury) in which witnesses are called and testimony is taken
	the range within which a voice can be heard
	an opportunity to state your case and be heard

sharp-eared (adjective)	hearing (adjective)
having keen hearing	able to perceive sound