VoiceOver > Audio Recording

Here is the helps page for third party installation for text to speech - https://helpx.adobe.com/captivate/using/slide-notes.html#using_third_party_voices_for_speech_text

Computerized voices typically are not liked by learners. The odd artifacts and pronunciations are a distraction. You can chase after different software packages, but wouldn't an actual human narrator just be easier? There are a few good use cases for a computerized voice, but I can only think of a few. If professional voiceover talent is too expensive for your budget, could you collaborate with another ID that has the tools and trade their voiceover skills for some lesson build skill you can exchange in return? That might help you meet a tight budget requirement. Perhaps even post here in the community as need arises. If you can specify male or female voice, language, style of narration/accent, and what you can offer as a trade, you may find a collaborator that you like and can just work directly with the ID from there.