front vowel vs vowel sound

front vowel and vowel sound both are nouns.

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

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

front vowel: (phonetics) Any vowel sound produced in the front of the mouth.
vowel sound: a speech sound made with the vocal tract open

Other hypernyms of front vowel include vowel.

front vowel (noun)	vowel sound (noun)
(phonetics) Any vowel sound produced in the front of the mouth.	a speech sound made with the vocal tract open