Do goodbye and soon have the same vowel sound?

No, "goodbye" and "soon" do not have the same vowel sound.

* Goodbye: The vowel sound in "goodbye" is similar to the vowel sound in the word "pie". It's a long "i" sound.

* Soon: The vowel sound in "soon" is similar to the vowel sound in the word "book". It's a short "oo" sound.