oral vowel vs vowel sound

oral vowel and vowel sound both are nouns.

Word	Noun	Adjective	Verb	Adverb
oral vowel	Yes	No	No	No
vowel sound	Yes	No	No	No

As nouns, vowel sound is a hypernym of oral vowel; that is, vowel sound is a word with a broader meaning than oral vowel:

oral vowel: (linguistics) an ordinary vowel that is produced without nasalization.
vowel sound: a speech sound made with the vocal tract open

Other hypernyms of oral vowel include vowel.

oral vowel (noun)	vowel sound (noun)
(linguistics) an ordinary vowel that is produced without nasalization.	a speech sound made with the vocal tract open