voice box vs speech organ

voice box and speech organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
voice box	Yes	No	No	No
speech organ	Yes	No	No	No

As nouns, speech organ is a hypernym of voice box; that is, speech organ is a word with a broader meaning than voice box:

voice box: a cartilaginous structure at the top of the trachea; contains elastic vocal cords that are the source of the vocal tone in speech
speech organ: any of the organs involved in speech production

Other hypernyms of voice box include organ of speech, vocal organ, cartilaginous structure.

voice box (noun)	speech organ (noun)
a cartilaginous structure at the top of the trachea; contains elastic vocal cords that are the source of the vocal tone in speech	any of the organs involved in speech production