anytime. it will distract your subconscious mind from watching your voice, it will help you to create your own vibe and be in it, and tbh i seen this tip in the movie "King's Speech" at the beginning when the coach put headphones with loud music on it on the king, he didn't hear his voice, but he read the speech very fluently, the coach recorded it and gave it to him on a vinyl, he didn't believe he spoke fluently, after a while, he listened to himself in shook, so why not?! same thing, with this technology, we can do better.