Not authentic. Capone had the ego, and the opportunity, to record himself, but never did. All the motion-picture footage of him is silent. And, recording tape did not exist in the 1930s, at least in America. Non-motion-picture sound recording at the time was done on disc, or wire recorders.
It’s a voice reconstruction by one of his family members, not his real voice, no real recording of his voice exists, if you want to check out her book, it’s called “uncle Al capone”, there’s a few interviews with her on RU-vid if your intrested
