Almost none, at most as little as a professional impersonator requires. GPT-4o's advanced voice mode would clone the user's voice by accident. A recording clip of one incident is available:

>During testing, we also observed rare instances where the model would unintentionally generate an output emulating the user’s voice.

>Example of unintentional voice generation, model outbursts “No!” then begins continuing the sentence in a similar sounding voice to the red teamer’s voice

https://assets.ctfassets.net/kftzwdyauwt9/4CG0G7y9WOfEkzBpi7...

https://openai.com/index/gpt-4o-system-card/