Here is the full list of all 8 VoiceStudio achievements worth 50 gamerscore. It takes around 1-2 hours to unlock all of the achievements on Xbox One.
You have said and uploaded the phrase to turn Xbox on 20 times.
You have completed and uploaded seven collections.
You have completed and uploaded five collections.
You have completed and uploaded three collections.
You've said and uploaded 20 phrases that start with the word "Xbox."
You have said and uploaded 20 phrases for game and app menus.
You have said and uploaded at least 20 phrases from Xbox One games.
You have completed and uploaded your first collection.