high frequency vs high pitch

high frequency and high pitch both are nouns.

Word	Noun	Adjective	Verb	Adverb
high frequency	Yes	No	No	No
high pitch	Yes	No	No	No

As nouns, high frequency and high pitch are synonyms defined as:

high frequency and high pitch: a pitch that is perceived as above other pitches

high frequency (noun)	high pitch (noun)
a pitch that is perceived as above other pitches	a pitch that is perceived as above other pitches
3 to 30 megahertz