output-to-input ratio vs frequency response

output-to-input ratio and frequency response both are nouns.

Word	Noun	Adjective	Verb	Adverb
output-to-input ratio	Yes	No	No	No
frequency response	Yes	No	No	No

output-to-input ratio (noun)	frequency response (noun)
the output power of a transducer divided by the input power	(electronics) a curve representing the output-to-input ratio of a transducer as a function of frequency