low frequency vs low pitch

low frequency and low pitch both are nouns.

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

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

low frequency and low pitch: a pitch that is perceived as below other pitches

low frequency (noun)	low pitch (noun)
a pitch that is perceived as below other pitches	a pitch that is perceived as below other pitches
30 to 300 kilohertz