spoken language vs voice communication

spoken language and voice communication both are nouns.

Word	Noun	Adjective	Verb	Adverb
spoken language	Yes	No	No	No
voice communication	Yes	No	No	No

As nouns, spoken language and voice communication are synonyms defined as:

spoken language and voice communication: (language) communication by word of mouth

Other synonyms of spoken language include language, oral communication, speech, speech communication, spoken communication.

spoken language (noun)	voice communication (noun)
(language) communication by word of mouth	(language) communication by word of mouth