Hmmm, I know what you are getting at Jeneane, but I am not sure how much I subscribe to the One True Voice theory.
I too play the silly game of pretending to be somebody else for money - and it is in that situation that part of the problem of voice lies. By assuming different voices during the course of a day I am tacitly admitting that I am not being true to myself (although I may be true to someone else's self!). The idea that there is, deep down there, one Voice that expresses the self perfectly is therefore tempting. It is a protection from the guilt of not telling the truth instilled from childhood.
If I consider the situations you mentioned, then there is a core within all these activities. However, I believe that my reactions and my voice are different. If all social mores and restrictions are ripped away, I believe I would emit a sound much like an over-lunched belch. Truthful, but not pretty in mixed company.
But before going any further it may be worth considering whether there is a cultural context here. There is a tendency among North Americans to have a greater dependency on 18th century Universal Truths than there is among Western Europeans (And for obvious reasons). We are a cynical, pragmatic lot over here. That is not a value judgement (it may not even be a valid judgement - or judgment). That could mean that when we start talking about the Voice, we are not using the same script.
So, let's agree that there is a Voice to some extent or other. But just because it is true, does that mean it is worth listening to? I can point to some very truthful individuals in that sense. They also happen to be complete tossers that I am not inclined to listen to.
Which leaves us with a slight problem. How do we get to the nitty gritty that is Andrew Arnold? And How do we know when we've found it?
But more to the point - is it worth looking for?