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 completed and uploaded five collections.
You have said and uploaded at least 20 phrases from Xbox One games.
You have completed and uploaded three collections.
You've said and uploaded 20 phrases that start with the word "Xbox."
You have completed and uploaded your first collection.
Complete and upload seven collections.
Say and upload 20 phrases for game and app menus across multiple collections.
Say and upload 20 phrases to turn Xbox on across multiple collections.