What is a vowel sound that repeated internally in words phrase?

You're asking about a vowel sound that's repeated within a word or phrase, right? It sounds like you're describing assonance.

Assonance is a literary device where vowel sounds are repeated in close proximity. It's used to create a musical effect and enhance the meaning of a word or phrase.

Examples:

* "The evil eat eat eat everybody." (The repetition of the short "e" sound)

* "I often observo the old oak tree." (The repetition of the long "o" sound)

Let me know if you'd like to explore other literary devices!