There are several reasons why Dr Joe's voice has evolved over the years during meditation. Our real time brain scans have shown that individuals do better and "go deeper" when certain voice techniques are used. Dr Joe intentionally makes his voice impersonal so that you can dissociate his voice from him. He also intentionally makes his voice sound as if it is coming from a distance and it feels like he is far away. When he raises his voice at times, he knows that it will keep people from falling in delta sleep patterns and therefore he sometimes wants people to linger in lighter brain wave states.
Below is a short video where Dr. Joe explains why he uses certain words, timing, tone and style of resonance he does in his guided meditations.