To get that default AI voice on a TikTok clip, you can use the app's built-in text-to-speech feature. When you're editing a video, just tap the "Text" button and type out what you want the AI voice to say. Then, select the text and choose the "Text-to-Speech" option from the popup menu. You'll see a few different voice options, including the default AI voice that you're probably thinking of. Just select that one and the AI voice will be added to your clip, it's pretty straightforward and works really well.