deafness vs tin ear

deafness and tin ear both are nouns.

Word	Noun	Adjective	Verb	Adverb
deafness	Yes	No	No	No
tin ear	Yes	No	No	No

As nouns, tin ear is a hyponym of deafness; that is, tin ear is a word with a more specific, narrower meaning than deafness:

Other hyponyms of deafness include tone deafness, deaf-muteness, deaf-mutism.

deafness (noun)	tin ear (noun)
partial or complete loss of hearing	insensitivity to the appropriateness or subtlety of language
	an inability to distinguish differences in pitch