chest voice vs chest register

chest voice and chest register both are nouns.

Word	Noun	Adjective	Verb	Adverb
chest voice	Yes	No	No	No
chest register	Yes	No	No	No

As nouns, chest voice and chest register are synonyms defined as:

chest voice and chest register: the lower ranges of the voice in speaking or singing

Other synonyms of chest voice include chest tone.

chest voice (noun)	chest register (noun)
the lower ranges of the voice in speaking or singing	the lower ranges of the voice in speaking or singing