audio vs audio frequency

audio and audio frequency both are nouns.

Word	Noun	Adjective	Verb	Adverb
audio	Yes	No	No	No
audio frequency	Yes	No	No	No

As nouns, audio and audio frequency are synonyms defined as:

audio (noun)	audio frequency (noun)
the sound elements of television	an audible acoustic wave frequency
a recording of acoustic signals
an audible acoustic wave frequency
the audible part of a transmitted signal