In this book, the author researches cases where people have heard a voice during emergency situations, which told them what to do to save their lives. He said the interesting thing is that each person he spoke to, when they thought about it, recognized the voice as their own. This tells me that the "Great Voice" they are hearing is that of their Double! He goes on to give advice on how to connect with the source of this voice and how to hear it regularly, not just during emergencies. Might be more interesting and helpful to those who are new to the path...

https://www.amazon.com/Clear-Hearers-John-DeSouza-ebook/dp/B0762HG79W