speech organ vs organ of speech

speech organ and organ of speech both are nouns.

Word	Noun	Adjective	Verb	Adverb
speech organ	Yes	No	No	No
organ of speech	Yes	No	No	No

As nouns, speech organ and organ of speech are synonyms defined as:

speech organ and organ of speech: any of the organs involved in speech production

Other synonyms of speech organ include vocal organ.

speech organ (noun)	organ of speech (noun)
any of the organs involved in speech production	any of the organs involved in speech production