The "normal" voice would probably be associated with clear diction, produced with the least physical effort based on the speakers physiology. Think sighing lou

The "normal" voice would probably be associated with clear diction, produced with the least physical effort based on the speakers physiology. Think sighing loudly but neutrally, producing white noise. Then sigh loudly again, tightening the vocal cords just enough to add sound, with the least effort. Try talking like that or near that where it feels comfortable. Wasted physical effort (in the sense of not adding clarity) in speaking is almost certainly culturally learned or due to the aesthetic/self-image of how one wants to hear oneself, attract and maintain listeners attention, differentiate oneself, etc.